A real test of the Pfizer COVID-19 vaccine in over half a million people confirms that it is very effective in preventing serious illness or death, even after a single dose.
The results published on Wednesday, resulting from a mass vaccination campaign in Israel, provide strong assurance that the benefits seen in smaller and limited tests persisted when the vaccine was used much more in a general population of different ages and conditions. of health.
The vaccine was 92% effective in preventing severe disease after two vaccines and 62% after one. Its estimated effectiveness in preventing death was 72% two to three weeks after the first shot, a rate that can improve as immunity develops over time.
It seemed as effective in people over 70 as it was in younger people.
“This is extremely reassuring … better than I would have guessed,” said Dr. Gregory Poland of the Mayo Clinic.
Dr. Buddy Creech of Vanderbilt University agreed: “Even after a dose we can see great effectiveness in preventing death,” he said.
None of the doctors had a role in the Israeli study, but both are involved in other coronavirus vaccination activities.
Both doctors also said the new results could increase consideration of the delay in the second shot, as the UK is trying or giving a dose instead of two to people who have already had COVID-19, as it does. France, to extend limited supplies.
“I’d rather see 100 million people with a single dose than see 50 million people have two doses,” Creech said. “I see a lot of encouragement for a single dose” in the Israeli results, which were published in the New England Journal of Medicine.
The vaccine, developed by Pfizer and its German partner BioNTech, is administered under two shots, three weeks apart, in most countries.
The study was conducted by researchers at the Clalit Research Institute and Ben-Gurion University in the Negev in Israel, along with Harvard University in the United States. He did not report the safety of the vaccine, only the efficacy, but no unexpected problems occurred in previous tests.
The researchers compared nearly 600,000 people aged 16 and over in Israel’s largest health care organization who were shot in December or January with an equal number of people of similar age, gender and health who they 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% per week or more after the second dose.
The effectiveness was 74% after a single stroke and 87% after two to prevent hospitalization and 46% and 92% to prevent confirmed infection. Reducing infections gives hope that the vaccine can reduce 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 the vaccine.
Overall, the figures compare well with the 95% effectiveness after two doses that were observed in the limited tests that led U.S. regulators to authorize emergency use of the vaccine, Poland said. How much the benefits of a single dose would be was an important question, “and now there is some data” to help the debate, he added.
“Perhaps what needs to be done 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 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 some insight into the vaccine’s performance against it.
Earlier this week, two UK studies suggested benefits even after a dose of Pfizer vaccine or a different dose of AstraZeneca. The UK is delaying the second blow by up to 12 weeks after the first to try to give more people a certain level of protection.
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The Associated Press Department of Health and Science receives support from the Howard Hughes Medical Institute’s Department of Science Education. AP is solely responsible for all content.