A real test of Pfizer’s COVID-19 vaccine in more than half a million people confirms that it is very effective in preventing serious illness or death, even after a dose.
Today’s published results of a mass vaccination campaign in Israel give a strong guarantee that the benefits seen in smaller, limited tests persisted when the vaccine was used much more widely in a general population of varying ages and conditions. of health.
The vaccine was 92% effective in preventing serious illness after two injections and 62% after one. Its estimated effectiveness in preventing death was 72% two to three weeks after the first injection, a rate that may improve as immunity grows over time.
It seemed as effective in people over 70 as it was in younger people.
“This is extremely comforting … better than I could have imagined,” said Dr. Gregory Poland of the Mayo Clinic.
Dr. Buddy Creech of Vanderbilt University agreed: “Even after a dose, we can see very high effectiveness in preventing death,” he said.
Neither doctor played a role in the study of Israel, but both are involved in other coronavirus vaccine work.
Both doctors also said the new results could increase the consideration of postponing the second injection, as the UK is trying, or give one dose instead of two to people who have already taken COVID-19, as France is doing, to stretch limited supplies.
“I would rather see 100 million people receiving one dose than seeing 50 million people receiving two doses,” said Creech. “I see a lot of encouragement with a dose” in Israel’s results, published by the New England Journal of Medicine.
The vaccine, made by Pfizer and its German partner BioNTech, is administered in two injections, three weeks apart, in most countries.
The study was led by researchers from the Clalit Research Institute and Ben-Gurion University of the Negev, in Israel, with Harvard University, in the United States. He did not report the safety of the vaccine, only the efficacy, but no unexpected problems arose in previous tests.
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The researchers compared nearly 600,000 people aged 16 and over at Israel’s largest health organization who received vaccines in December or January with an equal number of people of similar age, sex and health who did not receive the vaccine. None of the participants had previously tested positive for the virus.
The vaccine was estimated to be 57% effective in preventing any symptoms of COVID-19 two to three weeks after the first dose and 94% one week or more after the second dose.
Efficacy was 74% after one injection and 87% after two for preventing hospitalization and 46% and 92% for preventing confirmed infection. The reduction of infections gives hope that the vaccine may contain the spread of the virus, but this type of study cannot determine whether this is the case.
There were 41 deaths related to COVID-19, 32 of them in people who were not vaccinated.
Overall, the numbers compare well to 95% effectiveness after two doses, seen in the limited tests that prompted US regulators to authorize emergency use of the vaccine, Poland said. How much benefit a dose would have been 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 as many people as possible … is to give everyone a dose as soon as possible. I think it is a very acceptable strategy to consider, ”said Poland.
Israel has already vaccinated almost half of its population. A new variant of the virus, first identified in the UK, became the dominant strain in Israel during the study, so the results also provide some insight into the performance of the vaccine against it.
Earlier this week, two studies in the UK suggested benefits even after a dose of the Pfizer vaccine or a different dose of AstraZeneca. The UK is delaying the second injection by up to 12 weeks after the first to try to give more people some level of protection.
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