Covid-19: Pfizer vaccine efficacy was 52% after first dose and 95% after second dose, paper shows
BMJ 2020; 371 doi: https://doi.org/10.1136/bmj.m4826 (Published 11 December 2020)
Cite this as: BMJ 2020;371:m4826
The Pfizer and BioNTech covid-19 vaccine may provide some early protection, starting 12 days after the first dose, the peer reviewed results of a phase III trial have found.
The study, published in the New England Journal of Medicine,1 found that vaccine efficacy between the first and second doses was 52% (95% credible interval 29.5% to 68.4%), with 39 cases of covid-19 in the vaccine group and 82 cases in the placebo group.
Seven or more days after the second dose, vaccine efficacy then rose to 95% (90.3% to 97.6%), with eight covid-19 cases reported in the vaccine group and 162 cases in the placebo group.
The vaccine has so far been approved in Canada and in the UK, where it is already being rolled out to people over 80 and healthcare workers. In the US the Food and Drug Administration’s independent panel has voted in favour of emergency use authorisation for the vaccine, and the agency is expected to approve it within days.2