Alliance for Pandemic Preparedness

April 26, 2021

COVID-19 Vaccine Coverage in Health-Care Workers in England and Effectiveness of BNT162b2 MRNA Vaccine against Infection (SIREN): A Prospective, Multicentre, Cohort Study

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  • The Pfizer-BioNTech vaccine showed 70% effectiveness against SARS-CoV-2 infection 21 days after the first dose, and 85% effectiveness 7 days after two doses among staff working in publicly-funded hospitals in the UK. Participants were followed for two months, for a total of 1,106,905 person-days. During follow-up, 977 new infections occurred among unvaccinated individuals (14 per 10,000 person-days), compared to 71 infections 21 or more days after dose 1 in the vaccinated group (8 per 10,000 person-days) and 9 infections one week after the second dose (4 per 10,000 person-days). Among unvaccinated individuals who were infected, 543 (56%) had typical COVID-19 symptoms and 140 (14%) were asymptomatic within 14 days of testing positive, compared with infections in the vaccinated cohort, where 29 (36%) individuals had typical COVID-19 symptoms and 15 (19%) were asymptomatic.

Hall et al. (Apr 26, 2021). COVID-19 Vaccine Coverage in Health-Care Workers in England and Effectiveness of BNT162b2 MRNA Vaccine against Infection (SIREN): A Prospective, Multicentre, Cohort Study. The Lancet. https://doi.org/10.1016/S0140-6736(21)00790-X