Today, as predicted, Pfizer announced their plan to file for marketing authorization for their SARS-CoV-2 vaccine by the third week of November. As previously discussed, the difficult threshold for an approvable vaccine is: (1) enrolling and following up sufficient patients to obtain at least a two month safety database after a complete vaccination schedule; (2) at least a 50% rate of efficacy – prevention of serious disease; and, (3) a sufficient baseline incidence of COVID-19 in order to see efficacy in the enrolled patient population. FDA also recently added to the second requirement that prevented illness must include patients with serious illness in the control arm to demonstrate that the vaccine prevents both mild and severe illness.
Per today’s press release, the Pfizer vaccine will have met all these hurdles by the third week of November. The study has enrolled over 43,000 participants of whom Pfizer believes there are sufficient participants who will have the requisite two months. The vaccine was 90% effective with 94 confirmed cases of COVID-19 in the entire population of whom, by back calculation, 85 of the cases were in the placebo arm and 9 cases in the vaccinated arm. This remarkable efficacy obviates our previous concern about the baseline rate of infection which, in this particular study, was 0.2%. To that end, if the vaccine had had just a 50% efficacy rate, a higher rate of baseline infection might have been necessary to see statistically and clinically significant difference.
Pfizer anticipates having at least 50 million vaccine doses available before the close of 2020 with production of 1.3 billion doses in 2021.
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