A new study released this week from Israel’s Health Ministry found that while the Pfizer-BioNTech vaccine is highly effective at preventing severe COVID-19 cases caused by the delta variant, it was much less effective than the health agency previously thought at protecting people from infection.
The study, conducted from June 20 to July 17, with results released in a report Thursday, found that the two-dose Pfizer-BioNTech inoculation was roughly 88 percent effective.
At preventing hospitalization due to the delta variant and about 91 percent effective at protecting against severe cases.
However, the Israeli health agency said that for symptomatic COVID-19 cases, the vaccine was found to offer just about 41 percent protection against the delta variant, with an overall effectiveness of 39 percent for preventing delta variant infections.
The new percentage is much lower than the 64 percent effectiveness against delta variant infections that Israel reported earlier this month.
The previous figure drew widespread skepticism from health experts, who argued that mRNA vaccines like the Pfizer shot 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 released Wednesday in the New England Journal of Medicine that found that the two-dose Pfizer vaccine was 88 percent effective against the delta variant.
In comparison, the U.K. health agency said that the AstraZeneca vaccine was 67 percent effective at preventing infection from the delta strain.
Pfizer said in a Friday statement that it was confident in the protection offered by its two-dose vaccine, with BioNTech telling Bloomberg that it was reviewing the Israeli government’s data.
Israeli studies on the vaccine’s effectiveness against the delta variant were previously used by Pfizer earlier this month to suggest that people may eventually need a booster shot, though U.S. health officials have said it is not necessary at this time.
An advisory panel for the Centers for Disease Control and Prevention met Thursday morning to discuss whether it should recommend a booster COVID-19 shot for people who are immunocompromised.
