Pfizer vaccine works well in big ‘real world’ test
A real-world test of Pfizer’s COVID-19 vaccine in more than half a million people confirms that it’s very effective at preventing serious illness or death, even after one dose.
Wednesday’s published results, from a mass vaccination campaign in Israel, give strong reassurance that the benefits seen in smaller, limited testing persisted when the vaccine was used much more widely in a general population with various ages and health conditions.
The vaccine was 92% effective at preventing severe disease after two shots and 62% after one. Its estimated effectiveness for preventing death was 72% two to three weeks after the first shot, a rate that may improve as immunity builds over time.
It seemed as effective in folks over 70 as in younger people.
“This is immensely reassuring ... better than I would have guessed,” said the Mayo Clinic’s Dr. Gregory Poland.
Vanderbilt University’s Dr. Buddy Creech agreed: “Even after one dose we can see very high effectiveness in prevention of death,” he said.
Neither doctor had a role in the Israel study but both are involved in other coronavirus vaccine work.
Both doctors also said the new results may boost consideration of delaying the second shot, as the United Kingdom is trying, or giving one dose instead of two to people who have already had COVID-19, as France is doing, to stretch limited supplies.
“I would rather see 100 million people have one dose than to see 50 million people have two doses,” Creech said. “I see a lot of encouragement on one dose” in the results from Israel, which were published by the New England Journal of Medicine.
The vaccine, made by Pfizer and its German partner Biontech, is given as two shots, 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. It did not report on safety of the vaccine, just effectiveness, but no unexpected problems arose in previous testing.
Researchers compared nearly 600,000 people 16 and older in Israel’s largest health care organization who were given shots in December or January to an equal number of people of similar age, sex and health who did not receive vaccine. None of the participants had previously tested positive for the virus.