Pfizer (PFE.N)and partner BioNTech (22UAy.DE) plan to ask U.S. and European regulators within weeks to authorize a booster dose of its COVID-19 vaccine, based on evidence of greater risk of infection six months after inoculation and the spread of the highly contagious Delta variant.
The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) said, however, in a joint statement that Americans who have been fully vaccinated do not need a booster COVID-19 shot at this time.
The European Medicines Agency (EMA) said it was too early to determine whether more than the two shots that are currently required would be called for, saying it was confident for now that the established regimen was sufficient.
Some scientists have also questioned the need for booster shots.
Pfizer’s chief scientific officer, Mikael Dolsten, said the recently reported dip in the vaccine’s effectiveness in Israel was mostly due to infections in people who had been vaccinated in January or February. The country’s health ministry said vaccine effectiveness in preventing both infection and symptomatic disease fell to 64% in June.
“The Pfizer vaccine is highly active against the Delta variant,” Dolsten said in an interview. But after six months, he said, “there likely is the risk of reinfection as antibodies, as predicted, wane.” Data would be submitted to the FDA within the next month, he added.
Pfizer did not release the full set of Israeli data on Thursday, but said it would be published soon.
“It’s a small data set, but I think the trend is accurate: Six months out, given that Delta is the most contagious variant we have seen, it can cause infections and mild disease,” Dolsten said.
The FDA and CDC, in their joint statement, said: “We are prepared for booster doses if and when the science demonstrates that they are needed.”
Pfizer’s own data from the United States showed an erosion of the vaccine’s efficacy to the mid-80s after six months, Dolsten said, against the variants circulating there in the spring.
He stressed that data from Israel and Britain suggests that even with waning antibody levels, the vaccine remains around 95% effective against severe disease.
The vaccine, initially devised by Germany’s BioNTech, showed 95% efficacy in preventing symptomatic COVID-19 in a clinical trial the companies ran last year.
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