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Healthcare Provider Q&A

This Q&A document includes general information about COVID-19 vaccines and questions and answers specific to the vaccines currently in use in BC.
COVID-19 vaccine information is evolving, and as such, this Q&A may be updated as new information and new COVID-19 vaccines become available in BC.

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COVID-19 disease

Information on COVID-19 epidemiology is continually evolving. For the most up-to-date data on COVID-19 cases, go to:
While preventive measures such as physical distancing, frequent handwashing, and wearing a mask help to reduce the risk of exposure and transmission of SARS-CoV-2, the virus that causes COVID-19 infection and disease, these measures alone are not enough. The combination of COVID-19 vaccination and following BCCDC’s prevention measures offer the best protection from COVID-19.  Ending this pandemic requires all the tools we have available, including, most importantly, vaccination. 

COVID-19 vaccination protects not only the person being vaccinated, but also people around them, including those who are unable to get the vaccine. The more people in a community who are immunized and protected from COVID-19, the harder it is for COVID-19 to spread.
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Vaccine development and safety 

Factors that allowed COVID-19 vaccines to progress quickly include advances in vaccine development technology, government funding and purchase commitments, international collaboration among health professionals, researchers, industry and governments to develop the vaccines, rapid recruitment of participants for clinical trials, and streamlined vaccine approval processes by the regulatory body at Health Canada. Canada’s rigorous vaccine approval process has remained in place to assess COVID-19 vaccines. 

As for all vaccines and treatments that are authorized in Canada, Health Canada reviews the evidence and scientific data and decides whether to authorize the COVID-19 vaccine and will only do so when the evidence shows that the vaccine:
  • is safe, effective and of good quality and
  • demonstrates that the benefits outweigh the known and potential risks
Health Canada’s approval of the Pfizer-BioNTech vaccine on December 9, 2020 is an example of this accelerated process. Health Canada ensured that the Pfizer-BioNTech vaccine, laboratory studies and three phases of double-blind randomized clinical trials have shown safety, immunogenicity (ability to generate an immune response) and efficacy (ability to prevent COVID-19 disease) of this vaccine in animals and in adolescents and adults 16 years of age and older. Approximately 44,000 individuals randomized (1:1) to receive either the vaccine or placebo participated in phases 2 and 3 of the clinical trials.1  This population has been considered sufficient to approve vaccine based on safety and efficacy.

Health Canada also has processes in place to share information with other countries’ regulatory bodies including the US Food and Drug Administration and the European Medicines Agency. 

Once a vaccine is approved, vaccine safety and effectiveness are continuously monitored to detect rare serious or unexpected side effects.
The Biologic and Radiopharmaceutical Drugs Directorate (BRDD), which is part of Health Canada, supervises all aspects of vaccine production and quality control throughout the vaccine’s lifecycle. When a manufacturer develops enough scientific and clinical evidence of a vaccine’s safety, efficacy, and quality, they file a complete package of information that is submitted to BRDD for market authorization. A submission contains data from scientific studies, including laboratory and clinical studies, and information about the manufacturing process, including the manufacturing facility and manufacturing method. BRDD thoroughly reviews the submission to determine whether the benefits of a vaccine outweigh any potential risks. BRDD also reviews procedures for the manufacturer’s safety monitoring and any plans to minimize any identified risks. In addition, BRDD may visit the manufacturing site to evaluate the manufacturing process’ quality and make sure the manufacturer can carry out the necessary quality controls for the vaccine. 

The expedited review performed for COVID-19 vaccines has been possible because of a number of administrative changes to the process. These have included allowance of submission of data when available rather than the sponsor needing to wait until the entire data package is complete prior to submission. As well, for approval of these vaccines in Canada and many countries, there has been allowance for a shorter period of follow-up of people enrolled into the phase 3 clinical trials, whereas for non-pandemic vaccines, that follow-up period is typically upwards of one year. As a result, the clinical trials will continue to accrue cases and safety information for up to two years following immunization. Results from these studies will be reported in the future and will provide additional information about issues such as duration of protection from the vaccine(s).

For an effective conversation about COVID-19 vaccines, we can start from a place of compassion and understanding. Patients consistently rank healthcare providers as their most trusted source for vaccine information. Be transparent about the latest vaccine(s) information, reassure that we have a robust vaccine safety system in Canada, and emphasize vaccines’ role to protect recipients and the people around them. Your willingness to listen to the patients’ concerns will play a significant role in building trust in you and your recommendation. If a patient has concerns or questions, this doesn’t necessarily mean they won’t accept a COVID-19 vaccine. Sometimes patients simply want your answers to their questions. Once you’ve answered their questions, let them know that you are open to continuing the conversation. Encourage your patients to schedule another appointment or go to the BCCDC or ImmunizeBC websites for more information about COVID-19 vaccination. Continue the conversation about COVID-19 vaccination during future visits.

‎Canada has a system of local, provincial, and national surveillance to carefully monitor adverse events following immunization and detect any vaccine safety concerns. Once a vaccine is approved, its safety is continuously being monitored as long as it is used. In most provinces and territories, including BC, health care providers are legally obliged to report all serious and unexpected adverse events following immunization to the medical health officer. Every serious or concerning event is reported to the BC Centre for Disease Control (BCCDC). These reports are reviewed at BCCDC and also sent to the Public Health Agency of Canada system called the Canadian Adverse Events Following Immunization System (CAEFISS), as are reports from all provinces and territories. Additional monitoring for adverse events is being done through a system called CANVAS (Canadian National Vaccine Safety Network) through which recipients of the vaccine can enroll to self-report adverse events following receipt of the vaccine, with serious events being reported on to the regional health authority.

Vaccine safety is also monitored at the international level. The World Health Organization’s International Drug Monitoring Program collects reports from over 75 countries and uses these global data to monitor for any vaccine safety concerns. In addition, all vaccine manufacturers must report serious adverse events of which they become aware, in Canada or internationally, to Health Canada. For COVID-19 vaccines, manufacturers are expected to implement enhanced monitoring activities.

More information about the Canadian vaccine safety surveillance system is contained in the Canadian Immunization Guide, Part 2 – Vaccine Safety, Vaccine safety and pharmacovigilance

‎Vaccine providers should refer to the BC Immunization Manual, Part 5 – Adverse Events Following Immunization for criteria on reporting adverse events following immunization (AEFI), and report AEFIs to the regional health authority. Information on reporting can be found on the BCCDC’s Surveillance Forms page under Adverse Events Following Immunization.

For more information and details on how to report an AEFI in BC go to the BCCDC Reporting Adverse Events Following Immunization: For BC Community Vaccine Providers.


COVID-19 vaccines in Canada

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General questions

‎Yes, individuals should continue to practice recommended public health measures for the prevention and control of SARS-CoV-2 infection and transmission regardless of vaccination with COVID-19 vaccine. At this time, there is insufficient evidence on the duration of protection of COVID-19 vaccines in preventing infection and reducing transmission of SARS-CoV-2 to recommend discontinuation of public health measures.  It is expected, however, that over time with more information about the impact of vaccination on COVID-19 transmission that there will be changes to the current prevention and control measures. 


‎Vaccine efficacy is calculated using data from vaccine clinical trials. The median period of follow up of vaccine and placebo recipients from phase 3 clinical trials was 2 months. Additional information about the duration of protection will continue to accrue in the clinical trials which will gather data for at least two years. Vaccine effectiveness is calculated using real-world experience and data once a vaccine has been in use in diverse populations and settings. Vaccine effectiveness information continues to be obtained from post-marketing surveillance evaluations including studies using the test-negative design in populations being targeted for early vaccination such as health care workers, and eventually through the long-standing Sentinel Physician Surveillance Network (SPSN) in Canada, which uses the test-negative study design to assess seasonal influenza vaccine effectiveness and has been running in four provinces contributing data, led by BCCDC.

In B.C., research has shown that two doses of COVID-19 vaccine provides strong protection against infection and hospitalizations and that this protection has been maintained for at least four months. Two doses of either mRNA vaccine were more than 90% effective at preventing COVID-19 infection. Two doses of the AstraZeneca vaccine were more than 70% effective against infection. People who received one AstraZeneca dose followed by one mRNA vaccine dose had protection that was as good as with two mRNA doses. The vaccines are working similarly well in protecting against infections and hospitalizations due to the Delta variant, despite being more transmissible than other variants.

COVID-19 vaccine would only be contraindicated if the component the individual is allergic to is also present in the influenza vaccine. Influenza vaccine and COVID-19 vaccine ingredients vary depending on the specific product. Refer to the respective product monographs for each vaccine or go to the BC Immunization Manual, Part 4 – Biological Products, COVID-19 and influenza vaccine pages for ingredient lists. 

With the exception of FluLaval® Tetra, which contains polysorbate 80, none of the influenza vaccines contain the potential allergens that are in the mRNA vaccines (polyethylene glycol [PEG]) or viral vector based vaccines (polysorbate 80). In addition, the COVID-19 vaccines do not contain any of the potential allergens found in the influenza vaccines (e.g., ovalbumin/egg protein, thimerosal, gelatin, antibiotics). These vaccines may have some other components in common but these are not known to be allergens, i.e., sucrose and various salts. 

Yes. With GBS, typically the biological basis would have been an immune mediated reaction to the antigens in the vaccine. As these antigens are not shared across influenza and COVID-19 vaccines, GBS following receipt of an influenza vaccine is not a contraindication to receiving a COVID-19 vaccine.


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In B.C., individuals 5 years of age and older are eligible to receive COVID-19 vaccination. 

Clinical trials are underway to determine if COVID-19 vaccines are safe and effective in infants and children under 5 years of age. ‎

More information on COVID-19 vaccine eligibility can be found on the BCCDC website at: 
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COVID-19 mRNA vaccines (adult/adolescent)

Additional information specific to the mRNA vaccines currently authorized for use in Canada can be found in the National Advisory Committee (NACI) Statement, Recommendations on the use of COVID-19 Vaccines, Appendices A & B.

Messenger RNA (mRNA) is the ‘blueprint’ that cells use to synthesize proteins required for our physiology. The two newly approved COVID-19 vaccines use mRNA contained inside a lipid nanoparticle (LNP) that contains the synthetic nucleotide sequences that codes for the SARS-CoV-2 spike protein. After injection, the LNP is taken up by immune system cells, and once inside a cell, the mRNA provides the instructions that allow the cell to manufacture the spike protein. Once manufactured, the spike protein exits the cell, and becomes anchored onto the cell's surface. The immune system is activated to recognize the spike protein as foreign and initiates an immune response. The mRNA is then cleared by the cell’s natural mRNA degradation process. The estimated half-life for mRNA after injection is about 8-10 hours before degradation by native RNases (enzymes that break up the mRNA) in the body; the expressed spike protein persists in the body for several days and during this time continues to stimulate the immune response. mRNA vaccines are not live vaccines and cannot cause infection in the host. The delivered mRNA does not replicate, and does not enter the cell nucleus or interact with or alter the recipient’s DNA. 7, 8, 9     

Several mRNA vaccines are under development for other infections including cytomegalovirus, human metapneumovirus, parainfluenza virus type 3, Zika and influenza viruses.  

Manufacturing of mRNA vaccines has been under development for a decade. The process is cell-free (does not use human or other animal cells) and does not use vectors (like other viruses) or animal products, preservatives or adjuvants. 


Pfizer-BioNTech COVID-19 vaccine 

The estimated vaccine efficacy at least 7 days after Dose 2 was 94.6% (95% CI: 89.9 to 97.3%), with 9 laboratory confirmed symptomatic COVID-19 cases identified among vaccine recipients (N=19,965) compared to 169 cases among placebo recipients (N=20,172). The vaccine efficacy at least 14 days after Dose 2 in this population was comparable (94.4%, 95% CI: 89.1 to 97.3%). 

When stratified by age, vaccine efficacy against COVID-19 from 7 days after Dose 2 was between 93.7% (>55 years) and 95.6% (16 to 55 years). In individuals ≥65 years of age, vaccine efficacy was 94.7% (95% CI: 66.7 to 99.9%). In participants ≥75 years of age, the observed vaccine efficacy was 100% compared to placebo (95% CI: -13.1 to 100.0%), however this must be interpreted with caution as there were few cases identified in this age group, accounting for the wide confidence intervals. The estimated vaccine efficacy against confirmed COVID-19 from 7 days after Dose 2 was greater than 91% (between 91.7% and 100.0%) in all subgroups stratified by "at risk" status (e.g., presence of 1 or more comorbidities). The estimated vaccine efficacy against confirmed COVID-19 illness from 7 days after Dose 2 was greater than 89% for all races (89.3 to 100%) and 94% for all ethnicities included in the sub-analysis (94.4 to 95.4%).1

Moderna COVID-19 vaccine 

The estimated vaccine efficacy at least 14 days after Dose 2 was 94.1% (95% CI: 89.3 to 96.8%), with 11 confirmed COVID-19 cases identified among vaccine recipients (n= 14,134) compared to 185 confirmed COVID-19 cases among placebo recipients (n= 14,073). 

When stratified by age, vaccine efficacy against COVID-19 from 14 days after Dose 2 for those 18 to < 65 years of age was 95.6% (95% CI: 90.6 to 97.9%). For those > 65 years of age, vaccine efficacy was 86.4% (95% CI: 61.4 to 95.2%). For those > 75 years of age, vaccine efficacy was 100% however; this must be interpreted with caution as there were few cases identified in this age group.10

‎For both mRNA vaccines, SARS-CoV-2 binding and neutralizing antibodies were both induced by one dose of the vaccine and boosted by the second dose of the vaccine. Immunity after the first dose was seen beginning at around day 10 with the Pfizer vaccine and day 14 following the Moderna vaccine. Maximal immune response was seen 7 days after the second dose for each vaccine. 1, 8


‎1. Public Health Agency of Canada [Internet]. Ottawa (ON): Public Health Agency of Canada. Recommendations on the use of COVID-19 vaccines. Appendix A. 2021 Jan 12 [cited 2021 Jan 13]. Available from:

8. U.S. Food & Drug Administration [Internet]. Silver Spring (MD): U.S. Food & Drug Administration. 2020 meeting materials, vaccines and related biological products advisory committee December 10, 2020 meeting announcement. 2020 Dec 10 [cited 2021 Jan 5]. Available from:


Dosing and scheduling

Refer to the BC Immunization Manual Part 4 - Biological Products, COVID-19 vaccines for complete information on the COVID-19  mRNA vaccines prior to administration.

For optimal response, immunizers should observe recommended intervals as much as possible, however, doses given earlier than recommended may still be considered valid and need not be repeated if minimum intervals are observed. The recommended minimum intervals between doses for the COVID-19 mRNA vaccines are as follows:

  • Pfizer-BioNTech: 18 days 
  • Moderna: 21 days

NACI recommends that the vaccine series be completed with the same COVID-19 vaccine product. However, the spike proteins that encode the authorized mRNA vaccines have the same sequence and are stabilized in the same manner to remain in the pre-fusion confirmation, though other vaccine components like the lipid nanoparticle may be different.


If the vaccine product used for a previous dose is not known, attempts should be made to identify which vaccine was given for the first dose in order to give the same product for the second dose. If the same product is not readily available, the vaccine series can only be complelted with a similar type of COVID-19 vaccine (i.e., mRNA vaccine). Readily available means it is easily available at the time of vaccination without delay or vaccine wastage. Such a series should be considered as valid, without need to restart a two dose series with a new product. 

On June 1st 2021, NACI recommended that individuals who received a first dose of of the AstraZeneca or COVISHIELD vaccine could receive an mRNA vaccine for their second dose, unless there are contraindications to the mRNA vaccine.


Yes. A 21-gauge needle or narrower is recommended to prevent a larger opening in the vial stopper that may allow vaccine to leak.13

Yes. After adding the diluent into the vaccine vial, withdraw 1.8 mL of air from the vaccine vial into the empty diluent syringe prior to removing the needle and attached syringe from the vial.  This will prevent loss of vaccine from the vial through forceful expulsion under pressure.11 ‎


An additional dose can be withdrawn in its entirety, if the volume of residual vaccine allows, or constituted from up to three separate vials with residual vaccine, after withdrawal of the full number of labelled doses from the Pfizer (labelled 6 doses of 0.3 mL each/vial) or Moderna (labelled 10 doses of 0.5 mL each/vial or 14 doses of 0.5 mL each/vial for the US-labelled product) vaccines.


Following withdrawal of all available doses from each vial, the residual vaccine from up to three vials can be withdrawn into the same syringe to constitute a full dose provided the vials are from the same manufacturer and have the same lot number. More information can be found in the BC Immunization Manual, Part 4 – Biological Products: Pfizer-BioNTech and Moderna COVID-19 mRNA vaccines – Addendum: Pooling residual vaccine from up to three vials to constitute an extra dose.


Withdrawal of even 6 doses from a single vial of the Pfizer-BioNTech vaccine is dependent, in part, on the type of syringes or needles used to withdraw the vaccine from the vial. Low dead-volume syringes and/or needles should be used if available, as standard syringes and needles may not facilitate the extraction of the sixth dose from a single vial.  Similarly for Moderna, the withdrawal of a complete 0.5 mL dose after 10 or 14 doses have been removed from the vial is dependent, in part, on the type of syringes and needles, and low dead-volume syringes and/or needles may be needed to extract an additional dose.

Pain at the injection site is very common after the administration of the currently authorized COVID-19 mRNA vaccines, with more than 80% of recipients experiencing local injection site pain. Redness and swelling are also common.  Delayed local reactions including pain, redness, swelling, and occasionally pruritus, were observed in the Moderna clinical trials in about 1% of vaccine recipients, with onset on or after day 8 following vaccination. These delayed reactions were more likely to occur following the first dose than the second dose, and are thought to represent dermal hypersensitivity, typically resolving after 4-5 days. Vaccine recipients who have experienced these delayed local reactions have safely received the second dose.14, 15  These events are not reportable unless they meet the reporting criteria outlined in the BC Immunization Manual, Part 5: Adverse Events Following Immunization. 


Contraindications and precautions

Severe immediate allergic reactions such as anaphylaxis 

have been reported to be very rare following mRNA vaccination. As of October 22, 2021, NACI has made recommendations based on recent studies demonstrating that individuals who experienced anaphylaxis following their first dose of mRNA vaccine, were able to receive their second dose of mRNA vaccine with either mild or no side effects. NACI recommends that these individuals can safely receive future doses of mRNA vaccine provided there is:

  • consultation with an allergist or another appropriate physician before receiving future doses of a COVID-19 mRNA vaccine
  • a controlled setting where the vaccine can be administered with someone available who is experienced in managing anaphylaxis
  • an observation period of at least 30 minutes after vaccination (the normal observation period for people who have not experienced a severe immediate allergic reaction after vaccination is 15 minutes).
For a list of components in the vaccine and packaging consult the respective COVID-19 mRNA vaccine product monographs found at:

Both of the authorized COVID-19 mRNA vaccines in Canada contain polyethylene glycol (PEG) which can be found in various products such as: bowel preparation products for colonoscopy, laxatives, cough syrup, cosmetics, contact lens care solutions, skin care products and as an additive in some food and drinks. No cases of anaphylaxis to PEG in foods and drinks have been reported. ‎


In situations of suspected hypersensitivity or non-anaphylactic allergy to COVID-19 vaccine components, mRNA vaccination should be administered in a controlled setting with expertise and equipment to manage anaphylaxis, with an extended period of observation post-vaccination of at least 30 minutes.

Myocarditis is an inflammation of the heart muscle; if it is accompanied by pericarditis, an inflammation of the thin tissue surrounding the heart (the pericardium), it is referred to as myopericarditis. Symptoms can include shortness of breath, chest pain, or the feeling of a rapid or abnormal heart rhythm. Symptoms can be accompanied by abnormal tests (e.g., electrocardiogram, serum troponins, echocardiogram). These are inflammatory disorders of the outer lining of the heart and heart muscle, and occur for a variety of reasons including in association with viral infections.

As such, myocarditis can occur as a complication of COVID-19 infection. In Israel, COVID-19 infection has been estimated to cause myocarditis at a rate of 11 events per 100,000 persons among individuals aged 16 years and older. A retrospective study from the US found myocarditis (or pericarditis or myopericarditis) rates after primary COVID-19 infection to be as high as 45 cases per 100,000 patients in young males aged 12-17 years.  

Myocarditis/pericarditis following COVID-19 mRNA vaccines remains a rare adverse event following immunization (defined by the Canadian Immunization Guide as occurring at a frequency of 1 per 10,000 cases to less than 1 per 1,000 cases), even among the age groups where the highest rates of this event have been observed.17 Canadian data continue to show that with the primary series, the incidence of myocarditis is rare with either mRNA vaccine, but higher following the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30 mcg vaccine. In Canada, as of November 12, 2021, the overall reported rate of myocarditis/pericarditis was 3.0 per 100,000 doses administered following any dose of the Moderna 100 mcg vaccine compared to 1.9 per 100,000 doses administered following any dose of the Pfizer-BioNTech 30 mcg vaccine. The reported rates of myocarditis/pericarditis among males 18-29 years after the second vaccine dose were 15.9 per 100,000 for the Moderna 100 mcg vaccine and 2.6 per 100,000 for the Pfizer-BioNTech 30 mcg vaccine. These events are reported more frequently after the second dose and have been observed mostly in males 12-29 years of age, usually within a week of vaccination. Most cases have been mild and resolved quickly. 

Most cases recover fully with conservative treatment, with no serious outcomes. In BC, we have ensured that health care providers are aware of this observation and the possibility of it being causally linked to the vaccine, and how to diagnose and report this event when it occurs after mRNA vaccine. This is an emerging safety signal and will need to be studied further. 

In B.C., the Pfizer-BioNTech vaccine is preferentially recommended if available, for the primary series in individuals 12-29 years of age. While the risk of myocarditis and pericarditis continues to be a rare event following mRNA vaccination, there is a differentially lower risk of myocarditis and pericarditis following vaccination with Pfizer-BioNTech in comparison to Moderna. However, if the Pfizer-BioNTech vaccine is unavailable, or upon client request, the Moderna COVID-19 vaccine can be used provided informed consent includes the elevated risk of myocarditis associated with this vaccine. Individuals aged 30 and above should receive either mRNA vaccine (Pfizer-BioNTech or Moderna).

The second dose of COVID-19 mRNA vaccine should be deferred in those who experienced a physician-diagnosed myocarditis or pericarditis event following the first dose with no other cause identified, until further information about the risk of recurrence is available. Deferral is not required for those with a prior history of myocarditis or pericarditis that is unrelated to COVID-19 mRNA vaccines and are no longer being followed by a medical professional for heart issues.

Vaccine storage and handling

‎As neither mRNA vaccine contains preservatives to prevent microbial contamination, the Pfizer-BioNTech vaccine must be used within 6 hours of dilution and the Moderna vaccine must be used within 24 hours of first puncture to the vial.



For more information specific to receiving and handling the Pfizer-BioNTech and Moderna vaccines, refer to the BC Immunization Manual, Appendix E - Management of Biologicals, Guidance for Receiving and Handling the Pfizer-BioNTech COVID-19 mRNA vaccine (including dry ice procedures) and Guidance for Receiving and Handling the Moderna COVID-19 mRNA Vaccine. Additional information, including standard operating procedures can be found on the COVID-19 Immunize BC Operations Centre: Standard Operating Procedures page. 

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Booster doses

Completion of a primary COVID-19 vaccine series is highly effective against SARS-CoV-2 infection and associated outcomes such as hospitalization and morbidity. However, some individuals may experience decreasing levels of immunity over time, despite mounting an adequate immune response to vaccination. These individuals require a booster dose after completion of a primary COVID-19 vaccine series to restore protection. This is an important distinction from a third dose in a primary series that is recommend for moderately to severely immunocompromised populations, as these individuals require an additional dose to establish a strong immune response from the outset. In older adults, waning vaccine protection can be impacted by the ageing process and other underlying medical conditions. They may also live in congregate settings putting them at increased risk of COVID-19 infection. Individuals who received COVID-19 vaccination at shorter intervals between doses have been observed to have lower antibody titers compared to those who were immunized at longer intervals. Furthermore, the highly transmissible Delta variant has led to outbreaks and an increase in cases in specific settings and communities. Clinical trial data show that a strong immune response, effective against the wild type strain and Variants of Concern (VOC), was generated by a booster dose administered 6 months after completion of a primary series.28 To date, several countries have implemented booster dose programs, such as the U.S., the U.K., France, Germany and Israel.


‎To date, most studies examining the duration of protection have been based on manufacturer-recommended dosing intervals of 3 or 4 weeks between the first and second doses for mRNA vaccines. In B.C. and Quebec, data show that extended intervals between doses result in increased vaccine effectiveness against SARS-CoV-2 infection and COVID-19 related hospitalizations, when compared to shorter intervals. In addition, the emergence of the Delta variant and the increase in cases seen during the fourth wave of the pandemic have occurred simultaneously at a time of observed breakthrough cases in vaccinated individuals. It is difficult to ascertain whether this is due to depleting levels of vaccine protection in these individuals or if this is attributable to these individuals living within a community with lower vaccination levels. Despite some evidence of increasing risk of breakthrough infection over time, those vaccinated against COVID-19 with a two-dose series continue to demonstrate significantly lower odds of SARS-CoV-2 infection compared to unvaccinated individuals and, when infections occur, symptoms tend to be milder in vaccinated cases.28  Vaccine effectiveness against severe COVID-19 outcomes with all vaccine types (i.e., mRNA and viral vector vaccines) remains high, even in the context of the Delta variant. Several research and surveillance priorities will continue to occur with respect to the efficacy, effectiveness, immunogenicity and safety of the COVID-19 vaccines, which include population effectiveness and medium and long-term duration of protection of a complete series of COVID-19 vaccine. The degree to which these vaccines protect against COVID-19 one, two or more years after vaccination will be determined with ongoing vaccine effectiveness surveillance. 

In B.C., a booster dose of a COVID-19 mRNA vaccine is recommended for those who are 18 years of age and older at least 6 months after completion of the primary series.

Either Moderna or Pfizer-BioNTech COVID-19 vaccines may be used as a booster dose regardless of which COVID-19 vaccine was used in the primary series.

In addition, the Pfizer-BioNTech COVID-19 vaccine is preferred for the booster dose in those 18-29 years of age due to the lower risk of myocarditis/pericarditis with this vaccine. However, if the Pfizer-BioNTech vaccine is unavailable, or upon client request, the Moderna COVID-19 vaccine can be used provided informed consent includes the elevated risk of myocarditis/pericarditis
associated with this product. Individuals aged 30 and above should receive either mRNA vaccine (Pfizer-BioNTech or Moderna).

Refer to the BC Immunization Manual, Part 4 - Biological Products, COVID-19 Vaccines, COVID-19 Vaccine Eligibility for more information.

The recommended interval for a booster dose is at least 6 months after the primary series has been completed. Evidence from clinical trials showed a robust immune response in individuals who received a booster dose at least 6 months after completion of a primary series.28


A booster dose given with Pfizer-BioNTech vaccine is given as a full dose of 0.3 mL (30 mcg), the same as a dose within a primary series. However, a booster administered with Moderna vaccine will be given as a standard dose of 0.5 mL (100 mcg) to certain populations (e.g., individuals ≥ 70 years of age), while other individuals will receive a half dose of 0.25 mL (50 mcg). Refer to the BC Immunization Manual, Part 4 - Biological Products, COVID-19 Vaccines for further details.


Moderna filed submissions to Health Canada for regulatory approval for a booster dose at half the current dosage [i.e., a 50 mcg (0.25 mL) booster dose vs. 100 mcg (0.5 mL) primary series dose]. However, on October 29, 2021, NACI recommended that older adults may benefit from a 100 mcg (0.5 mL) dose of Moderna vaccine as a way to bolster the immune response from a booster dose. 

In B.C. it’s recommended that residents of long term care (LTC), assisted living and independent living facilities, alternate level of care clients awaiting placement in LTC and individuals 70 years of age and older who receive Moderna as a booster dose, should receive a full 100 mcg (0.5 mL) dose. All other individuals eligible for a booster dose that receive Moderna as their booster dose will receive a 50 mcg (0.25 mL) dose.28

If an eligible individual is receiving Pfizer-BioNTech vaccine as their booster, the dose is the standard 0.3 mL dose.

B.C. guidelines currently align with the Oct 29, 2021 NACI statement that recommends a 3-dose primary series for individuals who are moderately to severely immunosuppressed. As evidence around doses beyond a 3-dose series becomes available, changes to these guidelines may be forthcoming.

Initial results from studies that were sponsored by the manufacturers of mRNA vaccines suggest that reactogenicity from a third dose is similar to that from a second dose. However, these were studies of a small sample size (less than 350 participants in each study) with a short duration of follow-up.28

It is not yet known what the rate of myocarditis and pericarditis is after a booster dose with mRNA vaccine. Early data from Israel’s booster dose program show the rate following a booster as lower than with the second dose, but still increased when compared to rates following the first dose. Further studies into this are ongoing.

Pregnancy is a higher risk period for complications from COVID-19 infection, and pregnant people are more likely to be hospitalized and admitted to intensive care compared to their non-pregnant age-matched peers.  

Optimizing immunity against COVID-19 during pregnancy is desirable because serious illness during pregnancy can put both the pregnant person and the fetus at risk and may result in preterm birth, still birth or Caesarian section. COVID-19 immunization during pregnancy is safe for the pregnant person and for the fetus. No specific safety signals have been detected related to pregnancy.

Although, the primary indication for administration of COVID-19 vaccination is for maternal protection, IgG antibodies from the pregnant person are transferred to the fetus. This provides ‘passive immunity’ to the newborn, which may reduce the risk of infection for the infant during their first several months of life.

As there is a limited opportunity to provide protection during pregnancy, an earlier window for receipt of the booster dose has been enabled through the ImmsBC booking system. To receive a COVID-19 vaccine booster 8 weeks after their second dose, pregnant individuals will need to call the central call line (1-833-838- 2323) to book their appointment

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Pediatric COVID-19 mRNA vaccine

On November 19, 2021 Health Canada approved Pfizer-BioNTech COVID-19 (COMIRNATY®) vaccine (10 mcg) for use in children 5-11 years of age. The National Advisory Committee on Immunization (NACI) recommends that a complete series with Pfizer-BioNTech COVID-19 vaccine (10 mcg) may be offered to children 5-11 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose. 

In addition, Moderna’s mRNA COVID-19 (Spikevax™) vaccine for children 6-11 has been submitted to Health Canada for approval.
While most children do not become severely ill with COVID-19 disease, rarely some children may develop severe COVID-19 disease and require hospitalization. 

Children are also at risk of developing multisystem inflammatory syndrome in children (MIS-C), following infection with the SARS-CoV-2 virus. MIS-C is a rare but serious event that can occur several weeks following infection. As of November 2021, there have been a total of 19 cases of MIS-C in BC, seven of these cases occurred in children age 5-11. i

Children may also be at risk of a post COVID-19 condition known as long COVID or post-acute COVID-19 syndrome. While evidence is limited in pediatric populations, current evidence suggests the risk is lower in children compared to older age groups.

The Delta variant may pose a higher risk of infection for children due to its increased transmissibility, although the risk of severe disease in children does not appear to be increased with this variant. 

Though children were underrepresented in COVID-19 cases through the first three waves in Canada, this fourth wave is having a greater impact on those under 12 years of age. That is because this age group has not yet been able to be vaccinated and community transmission has continued with the gradual reopening of society. As of mid-November, children 5-11 years of age have the highest rate of COVID-19 cases across all age groups, although hospitalization rates have remained low.ii  

Throughout the pandemic, children have experienced social isolation, disruption to schooling and extra-curricular activities, which have had profound impacts on the mental and physical well-being of children and their families. These harms can disproportionately affect some children and families and may further exacerbate social inequities among some groups, including racialized and Indigenous communities, refugees and other newcomers to Canada, persons living in low-income settings, as well as children with disabilities.iii 

In addition, broad vaccination for COVID-19 is a critical tool to best protect everyone, especially those at highest risk, from severe illness and death. While following current public health measures, individuals who are fully vaccinated can safely resume many activities that they did prior to the pandemic.


As per the COVID-19 Situation Report week 45, since the beginning of the pandemic there have been 16,208 COVID-19 cases resulting in 160 hospitalizations, 16 ICU admissions and 2 deaths in children less than 10 years of age. There have been 24,108 COVID-19 cases which has led to 122 hospitalizations and zero deaths in older children and adolescents aged 10-19 years of age. There have been a total of 19 confirmed cases of Multi-system Inflammatory Syndrome in children and adolescents (MIS-C) in BC, with a median age of 9 (range 1-15) years. More information about COVID-19 cases in BC can be found on the BCCDC BC COVID-19 Data page.

Clinical trial data suggest the pediatric formulation of the Pfizer-BioNTech COVID-19 vaccine (10 mcg) produces a good immune response in children 5 to 11 years of age, similar to the response seen in young adults 16 to 25 years of age who receive the adolescent/adult formulation (30 mcg).

Preliminary efficacy of the 10 mcg dose vaccine against symptomatic COVID-19 in children 5 to 11 years of age is estimated to be 90.7%. 


The Pfizer-BioNTech pediatric dose is 10 micrograms of mRNA, one third of the 30 microgram dose given to adults and adolescents aged 12 and older. During the phase 1 study, a total of 48 children 5 to 11 years of age received 10 mcg, 20 mcg, or 30 mcg of the Pfizer-BioNTech (BNT162b2) COVID-19 vaccine (16 children at each dose level). On the basis of reactogenicity and immunogenicity, a dose level of 10 mcg was selected for further study.iv


No allergic events or anaphylactic reactions were reported after either dose. No serious adverse events (SAE) related to the vaccine, no cases of multisystem inflammatory syndrome in children (MIS-C), myocarditis/pericarditis or deaths were reported. Given the clinical trial was limited to 3,109 participants randomized to receive the Pfizer-BioNTech vaccine, it is unlikely that any adverse events occurring at a frequency less often than 1 in 1,000 would be detected.

Phase 2/3 of clinical trial data evaluated the frequency of adverse events in children aged 5-11 years based on the 10 mcg dose of Pfizer-BioNTech vaccine. Local reactions were common 1-2 days after any dose and resolved within 1-2 days. Systemic events were mild or moderate and in order of descending frequency included fatigue, headache, muscle pain, chills, fever and joint pain. Onset of systemic events were within 1-4 days after vaccine receipt with a median duration of 1 day. Systemic events were reported to be less severe for children 5-11 years of age who received the 10 mcg formulation of the Pfizer-BioNTech COVID-19 vaccine than in those aged 16-25 who received vaccination with 30 mcg. 

There were no reports of allergic or anaphylactic reactions after any dose. In addition, there were no reports of serious adverse events, and no cases of myocarditis/pericarditis. No deaths were reported. However, due to the number of participants (3,109 participants randomized to receive the Pfizer-BioNTech vaccine), the study was not powered to detect an adverse event occurring at a frequency of less than 1 in 1,000.
No cases of myocarditis or pericarditis were observed in the Pfizer-BioNTech clinical trial in children 5-11 years of age. However, due to the number of study participants in the clinical trial, adverse events occurring at a frequency at less than 1 in 1,000 may not have been detected.

Cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart) have been reported following vaccination with COVID-19 mRNA vaccines in Canada and internationally among individuals aged 12 years and older who received the 30 mcg formulation of the Pfizer-BioNTech COVID-19 vaccine or 100 mcg formulation of the Moderna COVID-19 vaccine; however, the risk is considered rare. 

Cases of myocarditis/pericarditis following COVID-19 mRNA vaccination occur most commonly in adolescents and young adults (12 to 30 years of age). It usually occurs within a week of vaccination and is more common:
  • after the second dose
  • in males than females
  • after Moderna than Pfizer-BioNTech vaccine.
The highest rate of myocarditis reported in Canada in association with the Pfizer COVID-19 mRNA vaccine has been for males aged 12 to 17 years following the 2nd dose, with about 7 cases per 100,000 doses. In both Canada and the US, no deaths attributed to the COVID-19 mRNA vaccine-related myocarditis have been identified in adolescents or young adults. 

Data from the US suggest the risk of myocarditis/pericarditis following mRNA COVID-19 vaccination may be higher in older adolescents aged 16-17 years compared to younger adolescents aged 12-15 years.V 

Symptoms of myocarditis/pericarditis can include shortness of breath, chest pain, or the feeling of a rapid or abnormal heart rhythm. Symptoms can be accompanied by abnormal test results (e.g., electrocardiogram, serum troponins, echocardiogram).vi  Available data indicate that most individuals affected have responded well to conservative therapy and have recovered quickly.iii

Emerging Canadian safety surveillance data suggest an extended interval between the first and second dose may reduce the risk of myocarditis/pericarditis associated with the second dose of an mRNA COVID-19 vaccine. For children 5-11 years of age the recommended interval between first and second dose is 8 weeks.iii

Myocarditis following mRNA COVID-19 vaccination tends to have a similar epidemiologic profile to classic myocarditis (unrelated to COVID-19), as it occurs more commonly in adolescents and young adult males. Classic myocarditis is less common in younger children 5-11 years of age.v

It is unknown whether myocarditis/pericarditis will occur after the lower doses of mRNA present within pediatric COVID-19 vaccines for children 5-11 years of age.iii

A Children’s Hospital of Philadelphia article states, “This situation may cause some parents to consider taking a “wait and see” approach, delaying their child’s vaccination until more doses have been administered. However, what many parents don’t realize is that in teens and young adults — the group with the highest occurrence of this side effect — the risk of developing myocarditis is greater following natural infection”. The article included the following estimates for myocarditis following COVID-19 mRNA vaccination compared to myocarditis following COVID-19 infection:

Of 100,000 males aged 16 to 29 years of age, approximately 5 would develop myocarditis after COVID-19 mRNA vaccination and about 59 would develop myocarditis after COVID-19 infection.

If we consider 100,000 females aged 16 to 29, 1 would develop myocarditis after vaccination and about 39 would develop myocarditis after COVID-19 infection.

As such, the risk of experiencing myocarditis is greater in an unvaccinated person than a vaccinated person. Therefore, opting to delay or forgo vaccination to avoid myocarditis is opting to take the risk of developing COVID-19 infection, which could put the child at greater risk of experiencing myocarditis.vii  
Yes. General immunization guidelines support the administration of a COVID-19 vaccine before, at the same visit, or after other vaccines at a different injection site(s) without regard to timing (this includes live and inactivated vaccines). If a client is due for more than one vaccine, providers are encouraged to offer all of the vaccines at the same visit. Concomitant administration of all recommended vaccines is important because it increases the probability that people will be fully vaccinated. It is also an important part of immunization practice if a healthcare provider is uncertain that a patient will return for additional doses of vaccine. This recommendation also aligns with the US CDC guidance.

While a small percentage (≤0.8%) of trial participants were administered a different non COVID-19 vaccine concurrently with the Pfizer-BioNTech vaccine or placebo, the impacts of this were not analysed or evaluated. However, a recent study evaluating the safety and immunogenicity of concomitant administration of COVID-19 vaccines with seasonal influenza vaccine in adults saw no safety concerns and that antibody responses to both vaccines were maintained.viii  NACI suggests that concomitant administration may contribute to erroneous attribution of an AEFI to a vaccine and may preferentially be avoided however, it may be warranted on an individual basis in some circumstances at the clinical discretion of the healthcare provider.iii

‎Tromethamine (Tris or trometamol) is used as a buffer in vaccines and medications, including those for use in children, to improve stability and prevent pH fluctuations in the solution. Tromethamine is widely used in several medications for topical, enteral or parenteral administration. It is also used in cosmetics as an emulsifier.ix No safety concerns have been identified with tromethamine. While tromethamine has been identified as a potential allergen, a review of existing evidence did not identify any cases of allergic reactions to tromethamine in children.iii Tromethamine in the Moderna COVID-19 vaccine has also been identified as a potentially allergenic excipient. However, there is increasing evidence that tromethamine is not the culprit excipient and/or the reactions are not IgE-mediated. This remains under investigation.x 

Even though severe outcomes from COVID-19 in children are uncommon, they can occur.  Vaccinating children helps keep them safe, and helps them keep vulnerable people in their community such as; older adults, younger children and infants and people with other health conditions safe as well.

The following are additional key messages to share with parents about COVID-19 vaccination for children aged 5-11:

  • Without vaccination, all children will likely contract the virus at some pointii
  • The benefits of vaccination will help protect their child from COVID-19 infection
  • Children who are infected with COVID-19 can develop multisystem inflammatory syndrome in children (MIS-C), a rare but serious condition. Although uncommon, as of November 2021, there have been 19 cases of MIS-C in BC related to COVID-19 infection, 7 of those in children aged 5-11. 
  • Their child's risk of severe outcomes from COVID-19 due to underlying medical conditions e.g., obesity, medically fragile/medical complexities, more than one underlying medical condition, neurological disorders, Down Syndrome and other immuno-compromising conditions
  • Children who are infected with COVID-19 may also develop a post-COVID condition also known as long-COVID or post-acute COVID in which symptoms such as: brain fog/cognitive issues, breathlessness, fatigue, can continue for weeks or months. More information about Post-COVID-19 Care & Recovery can be found on the PHSA website.
  • Benefits of vaccination also include:
    • Reduced time away from school or activities, with positive impacts on physical and mental health of children as a whole 
    • Reduces their child's risk of becoming infected due to exposure to COVID-19 through in-person activities such as school, extra-curricular activities and in the community, realizing that this changes with time
  • The unknown risk of exposure to COVID-19 variants in the future should also be considered
  • Their child’s risk of transmitting COVID-19 to close contacts who themselves are at higher risk of severe outcomes due to older age or underlying medical conditions ii
No. COVID-19 vaccines do not cause infertility and there is no scientific reason to believe that they will cause infertility. Recent studies have shown that COVID-19 vaccines do not impact fertility. xi xii  

The Society of Obstetricians and Gynaecologists of Canada (SOGC) addresses this online rumor in their recent statement stressing, “there is absolutely no evidence, and no theoretic reason to suspect that the COVID-19 vaccine could impair male or female fertility” and added, that “the widespread social media concern stems from misinformation about the similarities between syncytin-1 (used for placental implantation) and the SARS-CoV-2 spike protein. While the two proteins have several similar amino acids, they remain vastly different. The antibodies produced against the SARS-CoV-2 spike protein would not have cross-reactivity with syncitin-1.” xiii

Children who receive the 10 mcg Pfizer-BioNTech COVID-19 vaccine for their first dose and who have turned 12 years of age by the time the second dose is due should receive the 30 mcg Pfizer-BioNTech COVID-19 vaccine that is authorized for individuals aged 12 years and older to complete their primary series. If the second dose of 10 mcg is given, the dose should still be considered valid and the series complete. For more information refer to the Guidance Document on the Management of Inadvertent Vaccine Errors.

No. Children aged 5 to 11 are not required to show proof of vaccination.  

For more information go to the Proof of vaccination and the BC Vaccine Card page on the BC government website. 
i) BC Centre for Disease Control. COVID-19 situation report Week 45: November 07 – November 13, 2021. Available from: 

ii) Statement from the Council of Chief Medical Officers of Health (CCMOH): COVID-19 Vaccination in Children 5-11 years of age. Available from:

iii) National Advisory Committee o Immunization (NACI). November 2021. Recommendation on the use of the Pfizer-BioNTech COVID-19 vaccine (10 mcg) in children 5-11 years of age. Available from:

iv) New England Journal of Medicine. (November 9, 2021). Evaluation of the BNT162b2 COVID-19 Vaccine in Children 5 to 11 Years of Age. Available from: 

v) Oster, M. mRNA COVID-19 vaccine-associated myocarditis [slides presented at Advisory Committee on Immunization Practices (ACIP) meeting [Internet]. Atlanta (GA): Centers for Disease Control and Prevention (CDC); 2021 Nov 2 [cited 2021 Nov 10]. Available from:

vi) Brighton Collaboration. Myocarditis/pericarditis case definition [Internet]. Decatur (GA): The Task Force for Global Health; 2021 Jul 16. Available from:

vii) Children’s Hospital of Philadelphia. (Nov. 11, 2021). Feature Article: 3 Considerations for COVID-19 Vaccination of 5-11 year old Children. Available from: 

viii) Lazarus, R., Baos, S., Cappel-Porter, H., Carson-Stevens, A., et. al. (November 2021). Safety and immunogenicity of concomitant administration of COVID-19 vaccines (ChAdOx1 or BNT162b2) with seasonal influenza vaccines in adults in the UK (ComFluCOV): a multicentre, randomised, controlled, phase 4 trial. Available from: 

ix) Nilsson L, Csuth Á, Storsaeter J, Garvey LH, Jenmalm MC. Vaccine allergy: evidence to consider for COVID-19 vaccines. Curr Opin Allergy Clin Immunol. 2021 Aug 1;214:401,409. doi: 10.1097/ACI.0000000000000762.

x) Canadian Society of Allery and Clinical Immunology. (November 14, 2021). COVID-19 Vaccine Testing & Administration Guidance for Allergists/Immunologists from the CSACI. Available from:

xi) Bentov Y, Beharier O, Moav-Zafrir A, et al. Ovarian follicular function is not altered by sars-cov-2 infection or bnt162b2 mrna covid-19 vaccination. Hum Reprod. 2021. Available from: 

xii) Wang M, Yang Q, Ren X, et al. Investigating the impact of asymptomatic or mild sarscov-2 infection on female fertility and in vitro fertilization outcomes: A retrospective cohort study. EClinicalMedicine. 2021;38:101013. Available at

xiii) Society of Obstetricians and Gynecologists of Canada. (March 2021). Statement on COVID-19 vaccination and fertility. Available from: 
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Non-replicating viral vector-based (adenovirus) COVID-19 vaccines

AstraZeneca, COVISHIELD and Janssen COVID-19 vaccines

Both AstraZeneca and COVISHIELD COVID-19 vaccines are viral vector-based vaccines that contain a modified version of a replication-deficient chimpanzee adenovirus (ChAdOx1). The Janssen COVID-19 vaccine is also a viral vector-based vaccine which uses a modified replication-deficient human adenovirus type 26 vector. These are different viruses than the one that causes COVID-19. These vaccines stimulate the body's natural defenses to protect against the SARS-CoV-2 virus. Inside the shell of the modified virus, there is material from the virus that causes COVID-19. This is called a “viral vector.” Once the viral vector has entered the cells involved in the immune response, the genetic material gives the cells instructions to make the COVID-19 spike protein, the same antigenic target to which immunity is generated by the mRNA vaccines. The protein is produced intracellularly and placed on the surface of the cell, generating both cellular and humoral (T-lymphocytes and B-lymphocytes) immunity.‎



AstraZeneca/COVISHIELD COVID-19 Vaccine

The estimated vaccine efficacy at least 15 days after Dose 2 in study participants who received the standard dose (SD) vaccine for both doses was 62.5% (95% CI: 50.7 to 71.4%), based on identification of 71/6,085 (1.2%) cases in vaccine recipients and 186/6,073 (3.1%) in controls. The estimated vaccine efficacy by age was 63.1% (51.1 to 72.1%) in study participants 18-64 years of age and 50.7% (-65.8 to 85.4%) in participants ≥ 65 years of age (NACI). It is important to note, however, that Phase 3 clinical trials of the AstraZeneca vaccine had a very small number of participants over 65 years of age that contracted COVID-19 to determine the efficacy of the vaccine in this age group.


Estimates of vaccine efficacy against hospitalization > 22 days after dose 1 was 100% (NACI). 


An exploratory analysis examined the potential effect of the interval between dose 1 and 2 on vaccine efficacy in study participants receiving the SD/SD vaccine regimen. This analysis indicated that efficacy was higher in those with a longer interval (> 12 weeks) at 81.3% (95% CI 60.3 to 91.2).21


A further exploratory analysis at > 22 days after the first dose found that a single standard dose vaccine provided protection against primary symptomatic COVID-19 in the first 90 days with an efficacy of 76.0% (95% CI 59.3 to 85.9), with no evidence of waning of protection during the same time period.22


Because this vaccine was not tested in head to head clinical trials against the mRNA vaccines, the results of the efficacy studies are not directly comparable. The vaccines were studied in different populations at different times. Both of the mRNA vaccines and ChAdOx1-S vaccine provide high levels of protection against severe COVID-19 disease.

Janssen COVID-19 Vaccine

The estimates of vaccine efficacy against confirmed symptomatic moderate to severe/critical COVID-19 infection with onsets ≥14 days and ≥28 days post-vaccination are 66.9% and 66.1%, respectively.

The estimates of vaccine efficacy against confirmed symptomatic severe/critical COVID-19 infection are 76.7% with onset ≥14 days post-vaccination and 85.4% with onset ≥28 days post-vaccination. The efficacy against confirmed symptomatic severe/critical COVID-19 infection with onset ≥14 days was calculated for four age groups: 18–59 (80.5%), 18–64 (78%), ≥60 (68.5%), ≥65 (69.9%). For confirmed symptomatic severe/critical COVID-19 infection with onset ≥28 days, the efficacy calculated for the same age groups was: 18–59 (91.7%), 18–64 (92.9%), ≥60 (70.3%), ≥65 (50.1%).23

Dosing, scheduling and administration

Refer to the BC Immunization Manual, Part 4 – Biological Products, COVID-19 vaccines for complete information on the viral vector-based COVID-19 vaccines prior to administration.

AstraZeneca and COVISHIELD COVID-19 vaccines are interchangeable within the vaccine series, however, these vaccines are no longer being offered as a first dose, unless there is a contraindication to the mRNA vaccines, or as advised by the Medical Health Officer or an allergist. 

On June 1, 2021, NACI recommended that individuals who received a first dose of the AstraZeneca/COVISHIELD vaccine may receive either AstraZeneca/COVISHIELD vaccine or an mRNA vaccine (Pfizer-BioNTech or Moderna) for their second dose unless contraindicated.

In the event that an individual receives one dose of the AstraZeneca/COVISHIELD vaccine and is unable to receive the same type of viral vector vaccine for the second dose, receiving the Janssen vaccine would be considered restarting a vaccine series, as one dose of the Janssen vaccine is considered to be a complete series.

Individuals receiving the AstraZeneca/COVISHIELD and Janssen vaccines should be reassured that adverse events are very rare, and COVID-19 infections can lead to significant complications, including a range of clotting disorders. Those who have been vaccinated with either product in the last month, should monitor for symptoms and seek immediate medical attention in the very unlikely event that they develop: 

  • Prolonged headache beginning 4 or more days after vaccination
  • Blurred vision
  • Difficulty speaking
  • Seizure
  • Difficulty moving parts of the body 
  • Shortness of breath
  • Chest pain
  • New severe swelling, pain or colour change of an arm or a leg
  • Persistent abdominal pain
  • Abnormal bruising, reddish or purple spots or blood blisters under the skin
  • Bleeding beyond site of vaccination 
It is important to note that although rare, the outcome of TTS can be serious including fatal. In addition to timely diagnosis and management, clinicians who identify vaccine recipients with TTS should promptly report such cases to the adverse events following immunization system in B.C.

In B.C., these vaccines are no longer being offered as a first dose, and individuals who have received 1 dose of AstraZeneca or COVISHIELD vaccine may receive either AstraZeneca/COVISHIELD vaccine or an mRNA vaccine (Pfizer-BioNTech or Moderna) for their second dose, unless contraindicated.

Contraindications and Precautions

The AstraZeneca/COVISHIELD and Janssen COVID-19 
vaccines are contraindicated in individuals with:
  • A history of anaphylactic reaction to a previous dose of the vaccine or to any component of the vaccine.
  • A history of thrombosis with thrombocytopenia following a previous dose of an adenovirus vector COVID-19 vaccine. These individuals should be offered an mRNA vaccine, pending a hematologist's recommendation.
  • A history of capillary leak syndrome.
For a list of components in the vaccine see Section 6 Dosage Forms, Strengths, Composition and Packaging of the respective viral vector-based vaccine product monographs found at:


The AstraZeneca/COVISHIELD and Janssen COVID-19 vaccines contain polysorbate 80 which can be found in various products such as cosmetics and medical preparations including vitamin oils, tablets, and anticancer agents.

In situations of suspected hypersensitivity or non-anaphylactic allergy to COVID-19 vaccine components, consultation with an allergist is advised. If there is a specific concern about a possible allergy to a component of the COVID-19 vaccine being administered, an extended period of observation post-vaccination of 30 minutes may be warranted; alternately, the vaccine can be administered in an emergency room setting, also with a prolonged observation period.‎

In late March, a safety signal emerged in several European countries of an unusual syndrome of acute venous or arterial thrombosis, new onset thrombocytopenia with or without hemorrhage with onset of symptoms by around 14 days after vaccination with AstraZeneca COVID-19 vaccine. Affected sites have included central venous sinuses, portal vein, splanchnic veins, and splenic veins. While the first case reports appeared largely in young to mid-adult age women, later updates indicated the occurrence of the event in both sexes, although with a preponderance of cases in females under 55 years old. Because denominator data on vaccine recipients have not been made available, accurate assessment of rates by age group and sex has been hampered. 

In early April the European Medicines Agency issued a warning about the occurrence of this syndrome, with information for both clinicians and recipients.24  Subsequently Health Canada also added a warning for both AstraZeneca COVID-19 vaccine and COVISHIELD.25  Some countries have not reintroduced the use of the vaccine since the recognition of these events, and others have advised against use below a certain age. While the Canadian National Advisory Committee on Immunization has issued updated recommendations, which currently allow for immunization of those aged 30 and older in moderately high and high COVID-19 incidence communities, following a benefit-risk assessment,these

vaccines are approved for individuals aged 18 years and older. 

This adverse event has been called Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT), Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) and more recently Thrombosis with Thrombocytopenia Syndrome (TTS) and is estimated to occur in approximately 1 in 50,000 vaccine recipients. The frequency of TTS following a second dose of AstraZeneca or COVISHIELD vaccine is currently reported as approximately 1 per 600,000. Epidemiological information about the syndrome is still evolving, and a similar syndrome identified in the United States appears to be associated with the Janssen (Johnson & Johnson) adenovirus vector vaccine.26 The biological mechanism is thought to be similar to that of spontaneous heparin-induced thrombocytopenia, as it occurs outside of the context of heparin treatment. The Ontario Science Table COVID-19 Advisory has issued diagnostic and treatment guidelines.27 The Updated Recommendation for AstraZeneca and COVISHIELD Vaccines letter dated March 29, 2021 provides recommendations for physicians whose patients received COVISHIELD/AstraZeneca COVID-19 vaccine.

While not a contraindication, individuals who have experienced cerebral venous sinus thrombosis (CVST) with thrombocytopenia, unrelated to adenovirus vector COVID-19 vaccination, or heparin induced thrombocytopenia (HIT), should only receive an adenovirus vector COVID-19 vaccine if the benefits outweigh the potential risks and an mRNA vaccine is unavailable.


Immune thrombocytopenia (ITP) is a bleeding disorder resulting in a decreased number of circulating platelets. Cases of immune thrombocytopenia with very low platelet levels (<20,000 per µL) have been reported to be very rare events following vaccination with either the AstraZeneca or Janssen COVID-19 vaccines (defined by the Canadian Immunization Guide as occurring at frequency of < 1 per 10,000 events). These include cases with bleeding and cases with a fatal outcome. Some cases have occurred in individuals with a history of immune thrombocytopenia. Symptoms can include spontaneous bleeding, bruising and petechiae with onset usually within the first four weeks after receiving vaccination. If an individual has a history of ITP, the risks of developing low platelet levels should be considered before vaccination, and platelet monitoring is recommended after vaccination.


Those vaccinated with a COVID-19 viral vector vaccine should be instructed to seek immediate medical attention if they develop symptoms such as shortness of breath, chest pain, leg pain or swelling, or progressive abdominal pain following vaccination. Additionally, anyone with neurological symptoms after vaccination including sudden onset of severe headaches, persistent or worsening headaches, blurred vision, confusion or seizure, or who experiences spontaneous bleeding, unusual skin bruising or petechiae beyond the site of vaccination after a few days, should seek prompt medical attention.

Venous thromboembolism (VTE) is a disorder that includes deep vein thrombosis and pulmonary embolism. Venous thromboembolism has been observed as a rare event following vaccination with the Janssen COVID-19 Vaccine (defined by the Canadian Immunization Guide as occurring at frequency of 1 per 10,000 cases to less than 1 per 1,000 cases). Those vaccinated should be instructed to seek immediate medical attention if they develop symptoms such as shortness of breath, chest pain, leg pain, leg swelling, or persistent abdominal pain following vaccination with Janssen COVID-19 vaccine. In individuals with a pre-existing increased risk for thromboembolism, the possible increased risk of VTE with vaccine use should be considered. 


Vaccine storage and handling

‎The viral vector vaccines should be stored refrigerated at temperatures of +2°C to +8°C, similar to other routine non-COVID-19 vaccines in BC. Information regarding the storage and handling of refrigerated vaccines can be found in the BC Immunization Manual, Appendix E – Management of Biologicals.  

Additional information, including standard operating procedures (SOPs) can be found on the COVID-19 Immunize BC Operations Centre: Standard Operating Procedures page.

Additional information

The AstraZeneca/COVISHIELD and Janssen vaccines are manufactured using human embryonic cells for the propagation of the virus that contains the genetic information for the SARS-CoV-2 spike protein. The AstraZeneca/COVISHIELD vaccine uses the kidney cell line HEK-293 that was isolated in the 1970s while the Janssen vaccine uses the retinal cell line PER.C6 that was isolated in 1985. The cell lines are used widely in academic research and in the pharmaceutical and biotechnology industries. 

Although these cell lines are used in the manufacturing process, the final vaccine does not contain any cells.

The Catholic Church has stated that receiving a COVID-19 vaccine that required fetal cell lines for production or manufacture is morally acceptable.

‎The Serum Institute of India (SII) was founded in 1966 and is the world’s largest vaccine manufacturer. It produces more than 1.5 billion doses of vaccines each year. Vaccines from SII are used in national immunization programs in approximately 170 countries around the world. The vaccines used in these programs include diphtheria, tetanus, pertussis, Haemophilus influenzae type b, hepatitis B, measles, mumps and rubella. The SII is accredited by the World Health Organization and its facilities are compliant with good manufacturing practice (cGMP); this ensures that the vaccines manufactured by the SII are safe for use, contain the specified ingredients and have the required potency. 

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Special considerations

The following are recommendations for COVID-19 immunization in some specific populations who were either excluded from, or were represented by small numbers of participants in clinical trials. The recommendations for these groups are evolving, and more data have become available in the future about both protection from the vaccine and its safety. 

More information on COVID-19 considerations in these populations can be found under clinically extremely vulnerable individuals on the COVID-19 vaccination toolkit for health professionals page.

Pregnant and lactating people 

Althought the safety and efficacy of the COVID-19 vaccines were not studied in people who are pregnant or breastfeeding in the clinical trials for these vaccines, evidence during the post-marketing period has evolved. Outcomes in participants who became pregnant during the clinical trials and fetal outcomes are reported through registries, and real-world evidence (mostly with mRNA vaccination) has become available. While a cautionary approach has been taken historically to immunization during pregnancy and lactation, accumulating data on safety of immunization with a variety of vaccines during pregnancy and breastfeeding over several decades has led to expanded recommendations for use of vaccines in pregnancy. Both NACI32 and the Society of Obstetricians and Gynaecologists of Canada (SOGC)33 have pre-existing general recommendations that inactivated viral vaccines can be safely given in pregnancy. The SOGC recommends that pregnant people, those contemplating pregnancy, and those who are breastfeeding who are at high risk of infection and/or morbidity from COVID-19 should be offered the vaccine.34 New data have become available from postmarketing surveillance without safety concerns being identified. This includes a recently published US study of 35,691 women who self-enrolled into a safety surveillance program and 221 women who reported adverse events through the passive surveillance system.35  

Both NACI and SOGC recommend that the pregnant or lactating person be informed about the evidence on the safety of mRNA COVID-19 vaccines in these populations. This information should include the findings that in some studies, pregnant individuals with COVID-19 infection are at higher risk of invasive ventilation compared to non-pregnant age-matched individuals. Severe morbidity in pregnancy is associated with similar risk factors to those seen in non-pregnant people, including older age, asthma, obesity, diabetes, hypertension and heart disease. Emerging evidence suggests that COVID-19 mRNA vaccination during pregnancy is immunogenic and results in comparable anntibody titres to those generated in non-pregnant women. Regarding theoretical risks of vaccine receipt, the COVID-19 vaccines are not live virus vaccines, and there is not a basis to consider that these would be harmful neither to the fetus nor to the breastfed infant. A small number of pregnant women were inadvertently enrolled in the phase 3 clinical trials and are being followed to the end of their pregnancy to assess outcomes. 


Individuals who are immunosuppressed due to disease or treatment were not included in the initial COVID-19 vaccine clinical trials and as such there are limited data in these populations.7  Individuals who are immunosuppressed due to disease or treatment may have been observed to have a diminished immune response to the vaccine.

A primary series of three doses of an approved mRNA COVID-19 vaccine should be offered to individuals in the approved age group. For individuals who previously received a 1- or 2-dose complete COVID-19 series, an additional dose should be offered. In B.C., Moderna COVID-19 vaccine is preferentially recommended for all doses in the series. 

People living with stable HIV that are considered immunocompetent may receive the COVID-19 vaccine.7

Autoimmune disorders

Although participants with autoimmune conditions who were not immunosuppressed were not excluded from clinical trials of the vaccines, these constituted a very small proportion of trial participants and represent a very narrow range of autoimmune conditions. Specific conclusions about efficacy and safety, including risk of exacerbation of the condition, were not assessed. This theoretical risk of exacerbation was based on previous studies of mRNA vaccines designed for treatment of cancer and ability of the mRNA vaccines to elicit inflammation. The current mRNA COVID-19 vaccines have been optimized to reduce this risk.7

The Canadian Rheumatology Association recommends that on balance, a complete COVID-19 vaccine series should be offered to individuals otherwise eligible to receive the vaccine without additional barriers such as an individualized risk assessment or documented approval to proceed with immunization from their health care provider, with the exception of individuals on treatment with rituximab. Treatment with rituximab is expected to decrease effectiveness of the vaccine because of B-cell suppression. Such individuals should be off treatment for 5 months or longer prior to vaccination, and after vaccination, should not restart rituximab for at least 4 weeks in order to allow for adequate response to the vaccine. While other drug therapies for autoimmune disorders may reduce the immune response to the vaccine, most recipients will derive benefit from vaccination.36  

Individuals with autoimmune rheumatic diseases presenting for COVID-19 immunization who wish to proceed with vaccination, other than those treated with rituximab, should be offered immunization without referral to their health care provider. Those who are uncertain and wish to seek further advice can be referred to a decision aid developed by the Canadian Rheumatology Association with input from the Canadian Arthritis Patient Alliance. Alternately, they may prefer to have this discussion with their health care provider most familiar with their disease and treatment. 
To date, there is insufficient evidence on the receipt of both a COVID-19 vaccine and anti-SARS-CoV-2 monoclonal antibodies or convalescent plasma for treatment or prevention. Therefore, timing of administration and potential interference between these two products are currently unknown. Administration of these products close together may result in decreased effectiveness of a COVID-19 vaccine and/or anti-SARS-CoV-2 monoclonal antibodies because the monoclonal antibodies have high affinity for the spike protein expressed by the vaccines. 

For persons who received monoclonal antibodies or convalescent plasma for treatment of COVID-19, at least 90 days should elapse prior to vaccination with a COVID-19 vaccine.  A second infection is unlikely to occur in that time period, and a period of 90 days or more will minimize the risk of blunting of the vaccine induced immune response, accounting for the estimated half-life of these treatments. 

People receiving other antibody therapies unrelated to COVID-19 treatment (e.g., IVIG, RhoGAM) may receive COVID-19 vaccine at the same time or any interval before or after these therapies, as these are deemed unlikely to interfere with the immune response to the vaccine.

Yes. NACI recommends that a complete series with a COVID-19 vaccine should be offered to individuals with prior PCR-confirmed SARS-CoV-2 infection. Reinfections reported to date have been rare within the first three months following infection. Whether such individuals require the full two dose series is being studied; currently, the full series is recommended in BC. ‎


Yes. General immunization guidelines support coadministration of other indicated vaccines at the same visit, at a different injection site(s). This includes both inactivated and live vaccines, if the individual is behind schedule or due to receive these vaccines, and if these are not contraindicated in their circumstances. If not given at the same visit, these vaccines can be given before or after the COVID-19 vaccine, without regard to the number of days or weeks of this interval.

While formal studies of coadministration have not been conducted yet, general guidelines on immunization are to use every visit as an opportunity to offer recommended vaccines.

There are currently no data to inform whether COVID-19 vaccines affect TST or IGRA results. However, current knowledge about the immunologic response to COVID-19 vaccination is that it does not appear to impact TST or IGRA results. At the outset of the COVID-19 vaccination programs, there was a theoretical concern that COVID-19 vaccines may temporarily affect cell-mediated immunity, resulting in false-negative TST or IGRA test results.37

However, in cases where an opportunity to perform the TST or IGRA test might be missed, the testing should not be delayed since these are theoretical considerations. Therefore, TST and IGRA tests can be administered and read without regard to COVID-19 immunization. Re-testing
(at least 4 weeks post immunization) of individuals with negative results for whom there is high suspicion of TB infection may be prudent in order to avoid missing cases due to potentially false-negative results.7
If administration of the second dose of a COVID-19 vaccine is delayed, the second dose should be provided as soon as possible, and the series does not need to be restarted. In general, regardless of the time between doses, interruption of a vaccine series does not require restarting the series as delays between doses do not result in a reduction in final antibody concentrations for most other vaccines requiring more than one dose for a series. Maximum protection may not be attained until the complete vaccine series has been administered.

In BC, while vaccine supplies were limited, the time between first and second dose was extended to up to 4 months. This allowed a greater number of people to receive the important protection from a first dose of vaccine, given limited vaccine supply currently and high rates of COVID-19 transmission. The Canadian National Advisory Committee on Immunization (NACI) supported the delay of the second dose up to 4 months.38  

As of May 27, 2021, the recommended interval between dose 1 and dose 2 for the mRNA vaccines (Pfizer-BioNTech or Moderna) is 8 weeks. The recommended interval between dose 1 and 2 of the viral vector-based vaccines (AstraZeneca or COVISHIELD) is 8 to 12 weeks.

More information on the evidence and the decision to defer the second dose of COVID-19 vaccine in BC can be found in the Public health statement on deferral of second dose COVID-19 vaccine in BC.

Prophylactic oral analgesics or antipyretics (e.g., acetaminophen or non-steroidal anti-inflammatory drugs such as ibuprofen) should not be routinely used before or at the time of vaccination. While these medications may be used after vaccination (see below), it is not known whether these may blunt the antibody response to vaccine. This phenomenon has been observed in some studies of other vaccines in children, although its clinical significance is unknown.39, 40, 41 If an individual has taken one of these medications prior to immunization for any reason, they should be immunized as planned.  


Oral analgesics or antipyretics may be considered for the management of symptoms attributed to the vaccine (e.g., pain, fever, headache, myalgia) if these cannot be readily tolerated using non-pharmaceutical strategies.   

Lymphadenopathy (reactive adenopathy related to the immune response generated by the vaccine) in the regional nodes draining the deltoid area can occur. Such enlarged nodes may be viewed in imaging studies such as mammograms, and may be interpreted as abnormal and indicative of potential pathology. Some radiologists have recommended that routine imaging examinations including screening mammograms be scheduled before or at least 6 weeks after the vaccine dose in order to avoid misinterpretation of findings. 

The BC Cancer Agency recommends that scheduled screening mammograms should not be cancelled because of COVID-19 immunization. Those undertaking imaging within 6 weeks following vaccination should be asked for information about the site of vaccination so that this information can be recorded and considered in the interpretation of the radiograph. For those scheduling their appointments in conjunction with recent receipt or future scheduling of COVID-19 vaccine, this information should be provided to the booking clerk so that the screening appointment can be made before vaccination or 6 weeks after vaccination.42

Individuals for whom there are clinical indications (such as identification of a new breast mass or short-interval treatment monitoring or management of complications) for imaging should not delay imaging because of recent vaccination. 

For those being vaccinated in the context of suspect or known breast malignancy, the vaccine should be given in the contralateral arm for both doses.  
There have been increasing reports that some clients are requesting injection with aspiration. These requests are likely due to two recent studies in mice that seem to establish the possible link between small chances of vaccine leakage into the bloodstream and either rare instances of myocarditis or thrombosis with thrombocytopenia syndrome (TTS).     

As indicated in the BC Immunization Manual, Appendix B: Administration of Biological Products, aspiration prior to injection of a vaccine is no longer recommended as there are no large blood vessels at the recommended immunization sites and aspiration can increase pain resulting from the combined effects of a longer needle-dwelling time in the tissues and shearing action (wiggling) of the needle. Aspiration was originally recommended for theoretical safety reasons, however the veins and arteries within reach of a needle in the anatomic areas recommended for vaccination are too small to allow an intravenous push of vaccine without blowing out the vessel.

While there is no evidence to support the need for aspiration, there is no prohibition on aspiration when administering a vaccine. Therefore, to avoid barriers and missed opportunities for COVID-19 immunization, this procedure could be done to accommodate case-by-case requests. However, clients should be informed of the possibility of increased pain and discomfort at the injection site. Providing the rationale for not aspirating with injection may assist the client in making an informed choice on the procedure which may include the following information: 
  • There is no scientific evidence to support the need for aspiration 
  • There are no published reports of adverse effects associated with not aspirating 
  • The deltoid site used for intramuscular injection is not in close proximity to large blood vessels, therefore the possibility of inadvertently hitting a blood vessel is rare
  • For aspiration to be effective, it must be sustained for at least 5-10 seconds 
  • Injection with aspiration is more painful, likely because aspiration, when performed correctly for 5-10 seconds, results in longer contact time between the needle and the tissue and movement of the needle within the tissue during aspiration is expected
  • Bleeding at the injection site is common, and does not indicate incorrect injection technique or injection into a blood vessel
Needle aspiration is performed by pulling back on the plunger (applying negative pressure) of the syringe after inserting the needle into the client and prior to injecting the vaccine and includes the following steps:
  • After the needle pierces the skin, use the thumb and forefinger of the non dominant hand to hold the syringe barrel
  • Move the dominant hand to the end of the plunger 
  • Avoid moving the syringe 
  • Aspirate by holding the barrel of the syringe steady with your non dominant hand and by pulling back on the plunger with your dominant hand 
Effective aspiration may require 5 to 10 seconds prior to injection; if blood appears in the barrel of the syringe during this time, do not inject the vaccine and withdraw the needle, and properly discard the syringe. 

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Individuals who are immunocompromised

NACI strongly recommends that moderately to severely immunocompromised individuals in the authorized age group be vaccinated as follows:

Those who have not received a complete COVID-19 vaccine series:
  • Should be immunized with a primary series of three doses of mRNA vaccine.
Those who previously received a complete primary COVID-19 vaccine series (including one dose of Janssen vaccine, or a mixed series of mRNA / viral vector vaccines):
  • Should receive an additional dose of mRNA vaccine. 
In B.C., Moderna COVID-19 vaccine is preferentially recommended for all doses in the series.

In a meta-analysis of 22 studies (refer to the NACI statement and references therein) assessing seroconversion after the initial 2-dose series in immunocompromised and dialysis populations, Pfizer-BioNTech had slightly lower pooled rates of seroconversion than Moderna with relative risk of 0.94 (95% CI = 0.91 to 0.97) with moderate heterogeneity between studies (I2 = 65%, χ2 = 59.6, p˂0.0001).28 As such, Moderna vaccine is preferentially recommended for the third dose, which should be provided at least 28 days after the second dose. However if Moderna is unavailable, Pfizer-BioNTech should be given.
To date, people with moderately to severely compromised immune systems have been observed to generally have lower antibody responses and lower vaccine effectiveness from a complete 2-dose vaccine series (1-dose if vaccinated with Janssen vaccine) than immunocompetent individuals, although this varies depending on the underlying condition or immunosuppressive agents. 

Although the evidence is limited, observational studies show a reduction in vaccine effectiveness against SARS-CoV-2 infection and disease in immunocompromised adults when compared to the general population. A pooled analysis of three large population-based cohort studies 29, 30, 31 estimated vaccine effectiveness against any SARS-CoV-2 infection after the second dose in immunocompromised persons to be 79% (95% confidence interval (CI): 69-91%), compared to vaccine effectiveness after the second dose in the general population of 90% (95% CI: 86-95%).

The impact of immunocompromise on seroconversion after vaccination varies according to specific conditions and/or immunosuppressive therapy. Not all immunocompromised populations have been studied in detail. 

In addition, breakthrough infections (infection in fully vaccinated people) have occurred. This may be due to some degree of evasion of vaccine-induced immunity or waning of vaccine-induced immunity over time, or poor immune response to initial vaccine doses (as might occur amongst those who are moderately or severely immunocompromised). In order to reduce the risk of breakthrough infections among vulnerable groups several countries including Israel, the United States, France, Germany, the United Kingdom, Denmark and Norway have implemented, or are planning to implement, the administration of third doses of COVID-19 vaccine in some immunocompromised populations.

The additional dose of COVID-19 vaccine should be provided at least 28 days after the completion of the 2-dose series (1-dose if vaccinated with Janssen vaccine). Although studies on immunogenicity have shown that an interval longer than the minimum 28 days between doses is likely to result in a better immune response, use of an interval longer than 28 days should be considered against the risk of exposure to SARS-CoV-2 due to current epidemiology, variants of concern and the risk for severe disease. Some immunocompromised individuals may still be susceptible after the 2-dose primary series, so their period of susceptibility until receipt of the additional dose will also increase if the interval between doses is increased.

Third dose eligibility in B.C. is inclusive of all of the groups suggested for a third dose by NACI. The one major difference is that in B.C. we have made the decision to make patients who are on dialysis and/or with severe kidney/renal disease to be eligible for a third dose. This decision is based on rapidly growing literature that some patients undergoing hemodialysis had a poor antibody response to vaccinations (JAMA Network Open. 2021;4(9):e2123622. doi:10.1001/jamanetworkopen.2021.23622). 

We are also seeing within our BC data that dialysis patients who have completed a two dose COVID-19 vaccine series are being infected with COVID-19, indicating that their immune response may be insufficient. Other provinces, such as Quebec and Ontario, have been offering third doses to dialysis patients. 

Radiation therapy is commonly used for patients with solid or haematological malignancies. Radiation therapy can suppress lymphocyte counts for months to years after treatment in a dose and volume dependent fashion. After consultation with BC Cancer's radiation oncologists, it was decided that people who are undergoing radiation therapy would be eligible for a third dose to ensure that they develop a sufficient immune response.
There will be additional recommendations in the coming weeks for select groups of people who are immunocompromised.

The clinically extremely vulnerable (CEV) originally prioritized for COVID-19 vaccination included those people who would be more at risk of serious illness or hospitalization if they got COVID-19. However, many of the people in this group do mount a good immune response to the vaccine and are protected. 

Data now supports that a group of severely immunocompromised people whose immune response to a two-dose series is likely to be blunted, or not respond at all, should be offered a third dose to increase their chances of having a protective immune response with their initial vaccine series. 

Within the CEV group, there are people whose conditions made them at risk of serious illness if they got COVID-19 but whose condition does not prevent them from getting good protection through a good immune response from the two vaccine doses. People with these conditions do not require an additional dose. The evidence of vaccine effectiveness is reviewed closely for all CEV subgroups and the general population. If the evidence changes over time that will be considered in B.C.’s provincial vaccine strategy moving forward. 

Children aged 12 and older (born in 2009 and earlier) with the eligible conditions that make them moderately to severely immunocompromised are recommended a third dose. Clinical trials of COVID-19 vaccines for younger children (i.e., those born later than 2009) are still being conducted. 

In ten studies in adults, (five in solid organ transplant patients, three in patients on dialysis, one in patients with non-hematologic cancer and one in patients with hematologic cancer), the reactogenicity of a third dose of COVID-19 vaccine was similar to that of prior doses. In nearly all studies, the third dose was an mRNA vaccine, with the exception of one study where Janssen was also used for some study participations as an additional dose following a 2-dose mRNA COVID-19 vaccine primary series. However, there are no data specific to the Janssen COVID-19 vaccine when used as an additional dose in this population. No worsening of underlying disease was reported after immunization, however a few cases of graft versus host disease or organ rejection were reported. Without unvaccinated controls however, it is not possible at this time to determine if receipt of a third COVID-19 vaccine dose could potentially be associated with an increased risk of rejection in this population. No serious adverse events were deemed to be associated with the vaccine. Limitations of these studies include small sample sizes, short follow up periods and heterogeneous populations/vaccine schedules. Due to the small size of these studies and limited follow-up times, the impact of additional doses on rare adverse events in these populations are unknown.

The risk of myocarditis and/or pericarditis following receipt of an mRNA COVID-19 vaccine is currently reported more commonly after second doses compared to first doses. The risk of myocarditis and/or pericarditis associated with an additional dose of an mRNA vaccine, including when given to immunocompromised individuals, is unknown at this time. NACI is continuing to monitor the evidence and will update recommendations as information becomes available.

The additional or third dose recommended for moderately to severely immunocompromised persons should be distinguished from that of a booster dose. The intent of a booster dose is to restore protection that may have waned over time in individuals who responded adequately to an initial 1- or 2-dose primary vaccine series. Additional doses beyond the standard primary vaccine series, such as being recommended for those moderately to severely immunocompromised, provide an opportunity for individuals who may not have achieved an adequate level of protection from the standard primary vaccine series to develop a better immune response.


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Allergic event following a dose of COVID-19 vaccine

As of November 26, 2021 a total of 59,999,590 COVID-19 vaccine doses have been administered in Canada. There have been 27,747 adverse event reports with 21,304 considered non-serious and 6,443 considered serious. Of the serious reports, 671 severe allergic reactions or anaphylaxis have been detected for all COVID-19 vaccines across Canada. More information about reported adverse events following COVID-19 vaccine can be found on Health Canada’s Reported side effects following COVID-19 vaccination in Canada page. 

In BC, from December 13, 2020 to November 27, 2021 there have been a total of 8,625,058 COVID-19 vaccine doses administered. There have been 4,666 adverse events reported following COVID-19 vaccination with 339 meeting serious definition. These included 13 individuals admitted to hospital for anaphylaxis. There have been 426 reports of events managed as anaphylaxis (i.e., the client received epinephrine for a suspected anaphylactic reaction). Of these, 234 (55%) met the Brighton Collaboration definition for anaphylaxis with diagnostic certainty leves of 1, 2 or 3. Upon further review of these reports, many may reflect events such as anxiety or pre-syncopal (fainting) events. Refer to the Brighton Collaboration Anaphylaxis: Case Definition Companion Guide and the Anaphylaxis: Case Definition Pictorial Algorithm for additional information. More information about B.C.’s reports on adverse events can be found on BCCDC’s Vaccine Safety page. 

Recent reports of reactions to COVID-19 vaccines have increased concerns about their safety for individuals with allergies. The Canadian Society of Allergy and Clinical Immunology (CSACI) guidelines stress that there is a low risk for allergic reactions to vaccines and non-allergic reactions to vaccines are more common than allergic reactions. In addition, non-allergic reactions to vaccines also include anxiety-related adverse events that can mimic allergic reactions.43 It is important to note that other, less serious reactions may mimic allergic reactions such as vasovagal syncope which are not contraindications to further vaccination.44 

Additional information regarding allergies and COVID-19 vaccine for the public can be found in the CSACI’s COVID-19 Vaccines FAQ resource.
It is important to first determine whether the allergic 
reaction was an anaphylactic reaction. If an individual experienced a serious adverse event following immunization (AEFI) an AEFI report may be available in the provincial immunization data system. The AEFI report will contain details about the AEFI as well as the Medical Health Officer (MHO) recommendation on further immunization. 

Although anaphylaxis occurs rarely after vaccination it is potentially life threatening and requires immediate treatment. It is characterized by sudden onset, rapid progression of signs and symptoms and is set apart from simple allergic reactions by the simultaneous involvement of several organ systems. Anaphylaxis that has been proven to be causally associated with vaccines is estimated at a frequency of 1.3 episodes per 1,000,000 doses of vaccines administered.45 Very rare cases of severe immediate reactions (e.g., anaphylaxis) following vaccination with COVID-19 vaccines have been reported in countries throughout the world with an incidence estimated between 2 to 7.9 cases per million doses administered.46 There have been no fatalities nor long-term morbidity described with these events.47  

The checklist below can be used as a tool to assist health care providers to determine how to proceed when an individual reports an allergic reaction following a COVID-19 vaccine.
  • Was the reported event an anaphylactic reaction to a previous dose or any component of COVID-19 vaccine? 
  • Was the event reported to public health as an AEFI?
  • If reported to public health, is an MHO recommendation available? 
  • Did the MHO recommend a COVID-19 vaccine from a different vaccine platform? E.g., recommendation to administer a COVID-19 mRNA vaccine for someone who had an anaphylactic reaction to a COVID-19 viral vector vaccine.
A potential allergen found in the COVID-19 mRNA vaccines (Pfizer-BioNTech and Moderna) is polyethylene glycol (PEG). 
  • Polyethylene glycol (PEG) can also be found in: cosmetics, skin care products, contact lens care solutions, cough syrup, laxatives, and bowel preparation products for colonoscopy. PEG is also used as an additive in some processed foods and drinks. However, no cases of anaphylaxis to PEG in foods and drinks have been reported.
A potential allergen found in the COVID-19 adenoviral vector vaccines (AstraZeneca/COVISHIELD and Janssen) is Polysorbate 80. 
  • Polysorbate 80 can also be found in cosmetics and medical preparations which may include: vitamin oils, tablets, and anticancer agents.
More information and full lists of the components present in each COVID-19 vaccine can be found in the BC Immunization Manual, Part 4 – Biological Products, COVID-19 vaccines.

‎Very rare cases of severe immediate allergic reactions (e.g., anaphylaxis) have been reported following immunization with COVID-19 mRNA vaccines. History of an anaphylactic reaction to any component of the vaccine is generally considered a contraindication. However, for individuals with a history of anaphylactic reaction to a previous dose of an mRNA COVID-19 vaccine, administration of a subsequent dose in the series may be offered with the same vaccine or the same mRNA platform if a risk assessment deems that the benefits outweigh the potential risks for the individual and if informed consent is provided.  NACI states, “the risk of a severe immediate allergic reaction after re-immunization appears to be low and no long-term morbidity has been associated with re-vaccination.”48  In addition, recent studies have shown that most of the individuals who had these reactions after a previous dose of mRNA vaccine can be safely re-vaccinated with the same vaccine or another mRNA COVID-19 vaccine.49, 50, 51, 52 Prior to re-vaccination, the following steps are recommended:

  • Consultation with an allergist or other appropriate physician (e.g., medical health officer (MHO)) should be sought prior to re-vaccination.
  • If re-vaccinated, vaccine administration should be done in a controlled setting with expertise and equipment to manage anaphylaxis. Individuals should be observed for at least 30 minutes after re-vaccination. For example, a longer period of observation is warranted for individuals exhibiting any symptom suggestive of an evolving AEFI at the end of the 30 minute observation period.
Although such individuals may be offered a viral vector vaccine, re-vaccination with an mRNA vaccine is preferred due to the better effectiveness and immunogenicity of mRNA vaccines and the possible adverse effects specifically associated with viral vector vaccines (e.g., Thrombosis with Thrombocytopenia Syndrome [TTS]). 

If an adenoviral vector vaccine (e.g., AstraZeneca or Janssen) is recommended, the client should call 1-833-838-2323 and inform the agent that they have been recommended an adenoviral vector vaccine. Due to small supplies of these vaccines in the province, they will be added to a wait list for receipt of the respective vaccine. 

History of anaphylactic reaction to a previous dose of a COVID-19 viral vector vaccine or to any component of the vaccine is a contraindication to receiving a subsequent dose. These individuals should be offered a COVID-19 mRNA vaccine if a risk assessment deems that the benefits outweigh the potential risks for the individual and if informed consent is provided. If re-vaccinated, individuals should be observed for at least 30 minutes after re-vaccination. 


Any adverse event including an allergic reaction following a COVID-19 vaccine dose, should be reported to public health to be investigated by a medical health officer (MHO) or designate who will provide a recommendation on further vaccination. Adverse events following immunization (AEFI) reports and recommendations can be accessed from the provincial immunization data system. The individual who experienced an AEFI that was reported to public health will be notified of the MHO recommendations on further immunization. The MHO recommendations will also be sent to their most responsible health care provider. 

Any health professional who is aware of an adverse event following immunization must report the event to the medical health officer as per the Public Health Act. Information on AEFI reporting can be found on the BCCDC COVID-19 vaccination health care provider tool kit on the Adverse Events Following Immunization (AEFIs) page. More information about reporting anaphylaxis and other allergic reactions can be found in the BC Immunization Manual Part 5 - Adverse Events Following Immunization. In addition, the Report of Adverse Event Following Immunization with COVID-19 Vaccine is a one page form available that health care providers can use to report an AEFI with COVID-19 vaccines.


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2. Puranik A, Lenehan PJ, Silvert E, Neisen MJM Corchado-Garcia J, O'Horo JC et al. Comparison of two highly effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence. medRxiv. 2021 Aug 9. doi: 10.1101/2021.08.06.21261707:2021.08.06.21261707.

3. Nasreen S, Chung H, He S, Brown KA, Gubbay JB, Buchan SA, et al. Effectiveness of COVID-19 vaccines against variants of concern in Ontario, Canada. medRXiv. 2021 Jul 16. doi: 10.1101/2021.06.28.21259420.

4. Tang P, Hasan MR, Chematelly H, Yassine HM, Benslimane FM, Khatib HAA, et al. BNT1162b2 and mRNA-1273 COVID-19 vaccine effectiveness against the Delta (B.1.617.2) variant in Qatar. medRxiv. 2021 Aug 11. doi: 10.1101/2021.08.11.21261885.

5. Nanduri S, Pilishvili T, Derado G, Soe MM, Dollard P, Wu H, et al. Effectiveness of Pfizer-BioNTech and Moderna vaccines in preventing circulation of the SARS-CoV-2 B.1.617.2 (Delta) variant - National Healthcare Safety Network, March 1-August 1, 2021. MMWR Morb Mort Wkly Rep. 2021;70(34):1163-1166. doi: 10.15585/mmwr.mm7034e3.

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7. Public Health Agency of Canada [Internet]. Ottawa (ON): Public Health Agency of Canada. Recommendations on the use of COVID-19 vaccines. 2021 April 23 [cited 2021 April 28]. Available from:


8. U.S. Food & Drug Administration [Internet]. Silver Spring (MD): U.S. Food & Drug Administration. 2020 meeting materials, vaccines and related biological products advisory committee December 10, 2020 meeting announcement. 2020 Dec 10 [cited 2021 Jan 5]. Available from:


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11. Pfizer Canada ULC.  Pfizer-BioNTech COVID-19 Vaccine Product Monograph [Internet]. 2020 Dec 9 [cited 2021 February 19]. 26 p. Available from:


12. Moderna Therapeutics Inc. Moderna COVID-19 Vaccine  Product Monograph [Internet]. 2020 Dec 23 [cited 2021 Jan 5]. 19 p. Available from:


13. Pfizer-BioNTech COVID-19 Vaccine [Internet}. Kirkland (QC): Pfizer Canada ULC; c2021. Dosing and administration; 2020 Dec [cited 2020 Dec 22]. Available from:


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15. Blumenthal KG, Freeman EE, Saff RR, et al. Delayed Large Local Reactions to mRNA1273 Vaccine against SARS-CoV-2. N Engl J Med. Published online March 3, 2021:NEJMc2102131. doi:10.1056/NEJMc2102131


16. Canadian Society of Allergy and Clinical Immunology [Internet]. Orleans (ON): Canadian Society of Allergy and Clinical Immunology. SARS-CoV-2 vaccine testing & administration guidance for allergists/immunologists from CSACI. 2021 April 10 [cited 2021 April 29]. Available from:


17. Government of the United Kingdom. Medicines & Healthcare Products Regulatory Agency. Coronavirus vaccine - weekly summary of Yellow Card reporting. [Internet]; 2021 [cited 2021 Aug 30]. Available from:

18. Public Health Ontario. Myocarditis and Pericarditis Following Vaccination with COVID-19 mRNA Vaccines in Ontario. [Internet]; 2021 [cited 2021 Aug 30]. Available from:  

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22. Voysey M, Costa Clemens SA, Madhi SA, et al. Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: A pooled analysis of four randomised trials. Lancet [Internet]. 2021 Mar 6 [cited 2021 Mar 16];397(10277):881-891. Available from:


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25. Health Canada. Recalls and Safety Alerts. Health Canada provides update on the AstraZeneca and COVISHIELD COVID-19 vaccines. Updated April 16, 2021. Accessed April 28, 2021.,headaches%20or%20blurred%20vision%3B%20or

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