Largest real-world study of third dose of COVID-19 vaccine effectiveness

 

https://www.eurekalert.org/news-releases/933198

 

  News Release 29-Oct-2021
Peer-Reviewed Publication
Clalit Research Institute

Many countries are currently experiencing a resurgence of SARS-CoV-2 infections despite hitherto successful vaccination campaigns. This may be due to the greater infectiousness of the delta (B.1.617.2) variant of SARS-CoV-2, and to waning immunity of vaccines administered months earlier. In the face of the current resurgence, several countries are planning to administer a third booster dose of mRNA COVID-19 vaccine.

This study suggests that a third vaccine dose is effective in reducing severe COVID-19-related outcomes compared to individuals who have received two vaccine doses at least 5 months ago.

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The results show that, compared with individuals who received only two doses five months prior, individuals who received three doses of the vaccine (7 days or more after the third dose) had 93% lower risk of COVID-19-related hospitalization, 92% lower risk of severe COVID-19 disease, and 81% lower risk of COVID-19-related death. Vaccine effectiveness was found to be similar for different sexes, age groups (ages 40-69 and 70+) and number of comorbidities.

The study also included a population-level analysis which found that infection rates began to drop for each age group 7-10 days after that age group became eligible for the third dose.

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