Pfizer and BioNTech’s COVID-19 vaccine appeared to prevent the vast majority of recipients in Israel from becoming infected, providing the first real-world evidence that immunization will slow transmission of the coronavirus.
The vaccine, which is being administered in a national immunization program that began Dec. 20, was 89.4 percent effective in preventing laboratory-confirmed infections, according to a copy of a preliminary document posted on Twitter and confirmed by a person familiar with the job. The companies worked with the Israeli Ministry of Health on the preliminary observational analysis, which was not peer-reviewed. Some scientists questioned its accuracy.
The results, which were also reported in the magazine Der Spiegel, are the latest in a series of positive data that has emerged in Israel, the country that has administered the most vaccines in the world. Almost half of the population has received at least one dose. Separately, Israeli authorities said Saturday that the Pfizer-BioNTech vaccine was 99 percent effective in preventing deaths from the virus.
If confirmed, preliminary results on laboratory-tested infections are encouraging because they indicate that the vaccine may also prevent asymptomatic carriers from spreading the virus that causes COVID-19. This has not been clear because clinical trials testing the safety and efficacy of vaccines focused on the ability to stop symptomatic infections.
“This is the data we need to see to estimate the potential for achieving herd immunity with vaccines,” Raina MacIntyre, a professor of biosecurity at the University of New South Wales in Sydney, said in an email Monday. “However, we need to be able to see the data published in a peer-reviewed journal and to be able to examine the data in detail.”
Pfizer and BioNTech reported that they are working on a real-world analysis of the Israel data, which will be released as soon as it is completed. Spokesmen declined to comment on the unpublished data.
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