The coronavirus vaccine from Pfizer and BioNTech maintains 91.3% efficacy for at least six months after the second dose, even against the worrisome B.1.351 variant first identified in South Africa, the companies said Thursday. The findings—which double the previous best estimate of 90 days of protection, per CNN—come as researchers continue to track late-stage trial participants. Pfizer CEO Albert Bourla said the latest findings provide "further confidence in our vaccine’s overall effectiveness," per the Wall Street Journal. A day earlier, the companies announced the vaccine was 100% effective in preventing symptomatic disease in more than 2,200 children aged 12 to 15. The vaccine is approved in the US for those 16 and older, though that could soon change.
The new analysis covered 46,307 people enrolled in the Phase 3 trial, including more than 12,000 who received their second dose at least six months ago. Of 927 symptomatic COVID-19 cases observed through March 13, 850 were in people who'd received a placebo, while 77 were in people who'd been vaccinated, for that 91.3% efficacy rate. Of the 697 cases in US subjects, 647 were in people who'd received a placebo, for a 92.6% efficacy rate. Only nine cases were detected among 800 participants in South Africa, where the B.1.351 variant is dominant, and only in patients given a placebo. Overall, the vaccine was found to be 100% effective against severe COVID-19 as defined by the CDC and 95.3% effective against severe COVID-19 as defined by the FDA. CNN breaks down the differences, while USA Today reports the data is likely enough for the FDA to give the vaccine its "full approval." (Read more coronavirus vaccine stories.)