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Measuring Vaccination Impact & Coverage

COVID-19 vaccines continue to provide important protection again serious illness for all versions of COVID-19 including the most common variants of concern.

Last updated: March 8, 2022

Vaccine effectiveness measures how much protection a vaccine provides using data from use in the population.  Vaccine effectiveness reflects by how much the risk in the vaccinated is reduced compared to the risk in the unvaccinated.

B.C. continuously monitors COVID-19 vaccine effectiveness. We are still learning how our immune system responds to infection and immunization and how long immunity lasts after getting vaccinated

The vaccines continue to provide important protection against serious illness. People who have been vaccinated are much less likely to end up in hospital with COVID-19 than people who have not been vaccinated. Preventing serious outcomes is the main goal of the vaccine program.

Vaccine effectiveness results from B.C.

Booster doses and effectiveness against Delta and Omicron: February 2022

Updated estimates of vaccine effectiveness between September 2021 and February 2022 have been assessed when Delta and Omicron were the most common variants. This analysis compared the effectiveness in people who had received two doses of vaccine to those who had received a booster dose, including during the period when Delta dominated or Omicron dominated.

  • For Delta: Two doses provided excellent protection up to eight months after the second dose, particularly against severe outcomes:
    • Two doses prevented more than 90% of hospitalizations and more than 80% of infection.

  • For Omicron: Two doses provided good protection against severe outcomes
    • Two doses prevented about 65-75% of hospitalizations (reducing the risk of COVID-19 hospitalization by about two-thirds to three-quarters compared to unvaccinated people) 
    • Two doses were less effective against Omicron infection (less than 10-15% against any infection).

  • Booster doses: increased protection against both Delta and Omicron
    • Booster dose increased protection up to more than 95% against Delta infection or hospitalization.  
    • Booster dose increased protection up to more than 90% against hospitalization with Omicron and about 50-60% against Omicron infection.  
Two dose and effectiveness against Delta: October 2021

Infographic on vaccine effectiveness: Delta

Select to open

  • Vaccine effectiveness was monitored between May and September 2021 when Delta was the most common variant. This analysis measured the effectiveness of two doses of vaccines up to four months after the second dose.
  • Two doses prevent about 95% of COVID-19 hospitalizations. 
  • Two doses of either mRNA vaccine was more than 90% at preventing COVID-19 infection. Two doses of the AstraZeneca vaccine were more than 70% effective against infection. People who got one AstraZeneca dose followed by one mRNA vaccine dose (so-called “mix and match”) had protection that was as good as with two mRNA doses.
  • The vaccines protected against infections and hospitalizations due to the Delta variant, despite Delta being more transmissible than earlier variants.
  • Vaccine protection was stronger when people received their second dose more than six weeks after their first dose.

Learn more about the vaccine effectiveness findings.

Single dose and effectiveness against Alpha and Gamma: February 2021
  • A single dose of all vaccines available in B.C. (mRNA or AstraZeneca/COVISHIELD) protected well against hospitalization, reducing the risk by more than 80%, including among age groups at highest risk of severe outcome (50-69 year olds and those 70 years and older). Learn about the results.

  • A single dose of a COVID-19 mRNA vaccine reduced the risk of getting COVID-19 by two-thirds in adults 70 years of age and older during the peak of the spring 2021 wave in B.C. when Alpha (B.1.1.7) and Gamma (P.1) variants made up about 70% of circulating strains. Read the paper.

  • Risk reduced by 80% in long-term care residents and health care workers, the first people to be vaccinated in B.C. There was also a reduction in hospitalizations and deaths among vaccinated long-term care residents. Learn about the results.

Infographic: Vaccine effectiveness one dose Select to open

B.C. vaccination data  

COVID-19 Vaccination Coverage Dashboard provides:

  • Vaccination coverage for your health authority, community and by age. COVID-19 vaccination coverage is the percentage of people who have received one or more doses of COVID-19 vaccine in relation to the overall population.

Find the number of COVID-19 vaccine first and second doses administered in B.C. on the British Columbia COVID-19 Dashboard. Refer to the “Vaccine Information” tab on the bottom to see the number of doses administered (i.e. injected) and the number of doses distributed  (i.e. shipped to BC).


Vaccine efficacy vs. vaccine effectiveness

Vaccine efficacy and vaccine effectiveness are both measures of protection against a disease. 

Vaccine efficacy is calculated using data from vaccine clinical trials. 

Vaccine effectiveness is calculated using data from the population once a vaccine is approved and in use. It is more representative of all people and a diversity of situations and challenges. 

SOURCE: Measuring Vaccination Impact & Coverage ( )
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