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Two doses prevent about 95 per cent of COVID-19 hospitalizations: B.C. COVID-19 vaccine effectiveness results

​New results from the BC Centre for Disease Control (BCCDC) show that two doses of COVID-19 vaccines are providing strong protection, including against the Delta variant.
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​New results from the BC Centre for Disease Control (BCCDC) show that two doses of COVID-19 vaccines are providing strong protection, including against the Delta variant. This protection has been maintained for at least four months, with monitoring ongoing.  

Preventing serious outcomes is the main goal of the vaccine program. 

The B.C. analyses found vaccine effectiveness (VE) of 2 doses of any COVID-19 vaccine was about 95 per cent against hospitalization.

 Translated simply, this means that for every 100 hospitalizations due to COVID-19 in unvaccinated people, 95 could have been prevented through vaccination.

“Such vaccine protection is outstanding. It is deeply meaningful in preventing unnecessary suffering but also in sustaining critical health care system capacity,” Dr. Danuta Skowronski, principal investigator on the study and lead of the Influenza and Emerging Respiratory Pathogens Team at the BCCDC. 

Vaccine effectiveness (VE), including “mix and match”, against any  SARS-CoV-2 infection

The analysis also examined VE against any infection and found that receiving two doses of either mRNA vaccine was more than 90 per cent effective at preventing SARS-CoV-2 infection. Two doses of the AstraZeneca vaccine were more than 70 per cent 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. 

Any combination of vaccines, including two AstraZeneca doses, had a VE of about 95 per cent against hospitalization. 

Protecting against the more transmissible Delta variant

The Delta variant has been the most common type of COVID-19 virus circulating in B.C. since early July and now accounts for almost all infections. Among viruses genetically characterized in this BCCDC VE analysis, more than 90 per cent were the Delta variant.

Despite being more transmissible than other variants, the VE analysis shows the vaccines are working similarly well in protecting against infections and hospitalizations due to the Delta variant. 

Extending interval providing stronger protection

The results also examined the impact of extending the interval between dose one and dose two, a decision Canada made in the spring so that more people could get their first dose as soon as possible while vaccine supplies were limited. 

The findings showed that vaccine protection was even stronger when people received their second dose more than six weeks after their first dose.

“Extending the interval between doses was a doubly good decision: it ensured more people benefitted from substantial single-dose protection in the spring and may also have optimized second dose booster protection during the fourth wave, due to Delta, as we enter the fall,” said Dr. Skowronski.

No signs of waning 

The VE analyses show that strong protection of more than 80 to 90 per cent has been maintained at least four months after the second dose. The first groups to get vaccinated in B.C. were healthcare workers and older adults. These individuals were most at risk of acquiring and spreading COVID-19 or becoming severely ill.

In further VE analyses, findings show that strong protection is also maintained in health care workers and older adults living in the community. The team continues to monitor going forward.


 
 

 

 

SOURCE: Two doses prevent about 95 per cent of COVID-19 hospitalizations: B.C. COVID-19 vaccine effectiveness results ( )
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