Protection against symptomatic Covid-19 from Pfizer Inc. and partner BioNTech SE’s vaccine diminished over time but remained strong after six months, according to data released by the companies Wednesday.
The efficacy of the vaccine protecting against symptomatic disease dropped every two months, to 84% after six months from a peak of 96% within two months of vaccination, a decline that may add urgency to Pfizer’s push to administer an additional dose to maintain protection.
The companies reported that cumulatively the vaccine was 91% effective at preventing symptomatic Covid-19 during the first six months, in line with the analysis that was first reported earlier this year.
Pfizer plans to ask U.S. regulators next month to authorize booster shots of its vaccine, arguing that an additional shot may be needed to protect against the evolving virus. U.S. officials haven’t authorized the use of booster shots, although they are studying the issue.
Some countries have authorized booster shots for immunocompromised patients, but physicians and immunologists in the U.S. say there isn’t a clear answer yet on whether they are needed for the general population.
