Alliance for Pandemic Preparedness

May 28, 2021

Effectiveness of BNT162b2 and MRNA-1273 COVID-19 Vaccines against Symptomatic SARS-CoV-2 Infection and Severe COVID-19 Outcomes in Ontario Canada

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  • [Pre-print, not peer-reviewed] COVID-19 mRNA vaccines (Pfizer-BioNTech and Moderna) were 60% effective against symptomatic SARS-CoV-2 infection 14-20 days after the first dose and 91% effective ≥7 days after the second dose in a test-negative study among symptomatic adults in Ontario, Canada between December 2020 and April 2021 (n=324,033). Vaccine effectiveness against severe outcomes was 62% 14-20 days after the first dose and 98% ≥7 days after the second dose. First-dose vaccine effectiveness estimates were lower among adults aged ≥70 years, but comparable to younger individuals after the second dose. Two-dose vaccine effectiveness remained high against B.1.351 and P.1 variants with the E484K mutation.

Chung et al. (May 28, 2021). Effectiveness of BNT162b2 and MRNA-1273 COVID-19 Vaccines against Symptomatic SARS-CoV-2 Infection and Severe COVID-19 Outcomes in Ontario Canada. Pre-print downloaded May 28 from https://doi.org/10.1101/2021.05.24.21257744