|A healthcare worker prepares a Pfizer coronavirus disease (COVID-19) vaccination in Los Angeles, California, US, January 7, 2021. (Photo: Reuters)
Pfizer 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."
Pfizer's own data from the United States showed an erosion of the vaccine efficacy to the mid-80s after six months, Dolsten said, against the variants that were 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, developed with German partner BioNTech, showed 95% efficacy in preventing symptomatic COVID-19 in a clinical trial the companies ran last year.