The results published on Wednesday, from a mass vaccination campaign in Israel, give great certainty that the benefits observed in smaller and limited trials persisted when the vaccine was used much more widely in a general population of various ages and conditions. of health.
The vaccine was 92% effective in preventing serious illness after two shots and 62% after one. Its estimated effectiveness in preventing death was 72% two or three weeks after the first shot, a rate that can improve as immunity builds up over time.
It seemed as effective in people over 70 as it was in younger people.
“This is immensely reassuring … better than I would have imagined,” said Dr. Gregory Poland of the Mayo Clinic.
Dr. Buddy Creech of Vanderbilt University agreed: “Even after a dose we can see a very high effectiveness in preventing death,” he said.
Neither doctor played a role in the Israeli study, but both are involved in other coronavirus vaccine tasks.
Both doctors also said the new results could increase the consideration of delaying the second shot, as the UK is trying or giving a dose instead of two to people who have already had COVID-19, as France does, to stretch. limited supplies.
“I’d rather have 100 million people have a dose than see 50 million people have two doses,” Creech said. “I see a lot of encouragement in one dose” in the Israel results, published by the New England Journal of Medicine.
The vaccine, made by Pfizer and its German partner BioNTech, is given in two shots, three weeks apart, in most countries.
The study was led by researchers from the Clalit Research Institute and the Ben-Gurion University of the Negev in Israel, with Harvard University in the United States. He did not report vaccine safety, only efficacy, but no unexpected problems were raised in previous tests.
The researchers compared nearly 600,000 people aged 16 and over from Israel’s largest health organization who were shot in December or January with an equal number of people of similar age, sex and health who did not receive them. vaccine. None of the participants had tested positive for the virus before.
The vaccine was estimated to be 57% effective in preventing symptoms of COVID-19 two or three weeks after the first dose and 94% a week or more after the second dose.
Efficacy was 74% after one shot and 87% after two to prevent hospitalization and 46% and 92% to prevent confirmed infection. Reducing infections gives hope that the vaccine may slow the spread of the virus, but this type of study cannot determine if this is the case.
There were 41 COVID-19-related deaths, 32 of them in people who did not receive a vaccine.
Overall, the figures compare well with 95% effectiveness after two doses that were seen in limited testing that led U.S. regulators to authorize emergency use of the vaccine, Poland said. The amount of benefits there would be from a dose has been a big question, “and now there is some data” to help inform the debate, he added.
“Perhaps the right thing to do here to protect the maximum number of people … is to give a dose to everyone as soon as you can. I think it’s a very acceptable strategy to consider,” Poland said.
Israel has now vaccinated almost half of its population. A newer variant of the virus that was first identified in the UK became the dominant strain in Israel during the study, so the results also provide an idea of the vaccine’s performance against it.
Earlier this week, two UK studies suggested benefits even after a dose of the Pfizer vaccine or a different dose of AstraZeneca. The UK delays the second shot up to 12 weeks after the first to try to provide more people with a certain level of protection.
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