Pfizer‘s and BioNTech‘s Covid-19 vaccine is just 39% effective in Israel where the delta variant is the dominant strain, but still provides strong protection against severe illness and hospitalization, according to a new report from the country’s health ministry.
The efficacy figure, which is based on an unspecified number of people between June 20 and July 17, is down from an earlier estimate of 64% two weeks ago and conflicts with data out of the U.K. that found the shot was 88% effective against symptomatic disease caused by the variant.
However, the two-dose vaccine still works very well in preventing people from getting seriously sick, demonstrating 88% effectiveness against hospitalization and 91% effectiveness against severe illness, according to the Israeli data published Thursday.
“We have to be mindful that, with time, the effectiveness of these vaccines may wane,” said Dr. Isaac Bogoch, an infectious disease professor at the University of Toronto.
He stressed that the shots are still highly effective in preventing severe infection, helping hospital systems not get too overwhelmed heading into the colder months. That being said, “we’re still in the Covid era and anything can happen,” he said.
“We have to be prepared and we have to be nimble that people may need a booster at some point,” he added. “This close surveillance that’s happening in countries like Israel, the U.K. and other parts of the world is going to be very helpful in driving policy if and when we do need boosters.”
The delta variant, already in more than 104 countries, is concerning health officials in the U.S. as they see more breakthrough infections, which occur in fully vaccinated people, even though they are more mild.
White House chief medical officer Dr. Anthony Fauci said fully vaccinated people might want to consider wearing masks indoors as a precaution against the rapidly spreading variant in the U.S.
“That’s something we obviously don’t want to see,” Fauci said Wednesday, noting the so-called breakthrough infections. “This virus is clearly different than the viruses and the variants that we’ve had experience with before. It has an extraordinary capability of transmitting from person to person.”
The report out of Israel, which began vaccinating its population ahead of many other countries, is likely to bolster arguments from drugmakers that people will eventually need to get booster shots to protect against emerging variants.
Pfizer said earlier this month it is starting to see waning immunity from its two-dose vaccine, and now plans to seek authorization from the Food and Drug Administration for a booster dose. However, federal officials say fully vaccinated Americans do not need additional shots at this time.
In a statement to CNBC, Pfizer said it remains confident its two-dose regimen is protective against the coronavirus and its variants.
Still, it said a third dose may be helpful after analysis from its phase three study showed a decline in efficacy against symptomatic infection after four to six months.
“Initial data of a third dose of the current vaccine demonstrates that a booster dose given at least 6 months after the second dose elicits high neutralization titers against the wild type and the Beta, which are 5 to 10 times higher than after two primary doses,” the company said.