A third dose of COVID-19 vaccine effectively protects against the harmful effects of Omicron, at any level of disease severity, confirms in detail a new study from the National Institute of Public Health of Quebec (INSPQ).
The prevention of hospitalizations increases from 80% to 90% in people vaccinated three times, indicates the short scientific opinion made public on Wednesday.
This study is based on preliminary data collected between December 26, 2021 and February 5, 2022, i.e. when the Omicron variant was dominant in Quebec.
“The effectiveness of the vaccine in preventing an emergency room visit was approximately 60% after two doses and 85% after three doses,” the researchers mention.
Regarding the prevention of a “mild disease”, the effectiveness of the vaccine increases from 45% after two doses to 80% after three doses.
These statistical discrepancies are observed for all types of vaccine and all combinations, with the exception of that produced by AstraZeneca. “Efficacy is slightly lower in [les personnes] having received only two doses of the Vaxzevria/Covishield vaccine,” the study states.
The INSPQ results also confirm that the protection conferred by vaccines “remains rather stable” in the long term. A decrease of approximately 10% in protection against COVID-19 is observed after 32 weeks.
Nearly 45% of the Quebec population obtained a third dose, as of February 15.
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