The study, conducted from From June 20 to July 17, with results published in a report Thursday, found that the two-dose Pfizer-BioNTech inoculation was approximately 88% effective in preventing hospitalization due to the delta variant and approximately 91% to protect against severe cases.
However, the Israeli health agency said that for symptomatic cases of COVID-19, the vaccine has been shown to offer about 41% protection against the delta variant, with an overall effectiveness of 39% in preventing infections. with delta variant.
The new percentage is well below the 64% effectiveness against delta-variant infections reported by Israel earlier this month.
The previous figure sparked widespread skepticism from health experts, who argued that mRNA vaccines like the Pfizer vaccine have repeatedly been shown to offer strong protection against COVID-19 variants.
The initial Israeli report was also challenged by a Public Health England study published Wednesday in the New England Journal of Medicine which found that the two-dose Pfizer vaccine was 88% effective against the delta variant.
By comparison, the UK health agency said the AstraZeneca vaccine was 67% effective in preventing infection with the delta strain.
Ran Balicer, chairman of Israel’s National Expert Advisory Team on COVID-19 Response, said in a statement accompanied by Thursday’s report that their data could have been skewed, citing how groups of people vaccinated were tested against those who had not. been vaccinated.
“The strongly asymmetric exposure patterns during the recent epidemic in Israel, which are limited to specific population sectors and localities,” mean that certain factors may not be taken into account, he said, according to Bloomberg.
“We try to complement this research approach with others, taking into account additional personal characteristics,” Balicer added before noting that “it takes time and more cases”.
Pfizer said in a statement Friday that it was confident in the protection offered by its two-dose vaccine, with BioNTech telling Bloomberg it was reviewing Israeli government data.
Israeli studies on the efficacy of the vaccine against the delta variant were already used by Pfizer earlier this month to suggest that people may possibly need a booster, although U.S. health officials have said that no. was not necessary at the moment.
An advisory group from the Centers for Disease Control and Prevention met Thursday morning to discuss whether to recommend a COVID-19 booster for people with compromised immunity.