New regulatory filings show Pfizer had evidence, early into the vaccination campaign, that the efficacy of its COVID-19 vaccine waned, but the drug company waited months before alerting the public.
In late 2020, the airways became saturated with triumphant reporting of Pfizer and Moderna’s “95% effective” COVID-19 vaccines. Millions rolled up their sleeves with the belief that reaching herd immunity would end the pandemic.
But by June 2021, the pandemic endgame story had gone off script. Highly vaccinated countries like Israel were experiencing a new wave of COVID-19 infections, vaccination rates were starting to slow, and public skepticism was snowballing.
Authorities tried to allay fears by saying that new infections were “rare breakthroughs,” but the data became too difficult to ignore.
By early July, the Israeli Ministry of Health reported that vaccine effectiveness against infection and symptomatic disease had fallen to 64%. Three weeks later, revised estimates put Pfizer’s vaccine at just 39% effective.
Regulatory filings date-stamped from April 2021 show Pfizer had strong evidence that its vaccine’s efficacy waned — results the company did not publicly release until the end of July.
Peter Doshi, associate professor at the University of Maryland School of Pharmacy, accessed these documents from the Canadian drug regulator, Health Canada.