The coronavirus vaccine from Pfizer and BioNTech is extremely effective at preventing severe disease in a real-world setting, the companies said Thursday, and protection kicks in two weeks after the second dose.
The companies said an analysis of data from Israel showed the shot was at least 97 percent effective in preventing symptomatic disease, severe or critical disease and death, and that the impact from two doses is better than a single dose.
The findings essentially match the 95 percent efficacy the companies reported from the vaccine’s late-stage clinical trial in December, which set the stage for authorization in the U.S.
The data, which were announced in a press release and not peer reviewed, also showed that the vaccine was 94 percent effective at preventing asymptomatic infections, a crucial sign that it could be helping to limit transmission of the virus.
However, the companies noted that the effectiveness estimates may be affected by behavioral differences between vaccinated and unvaccinated persons, such as different test-seeking behaviors or levels of adherence to preventive measures.
In the clinical trials, randomization minimized the impact of differences between vaccinated and unvaccinated participants.
Israel has been leading the world in vaccinations and agreed to collect and share the real-world data from its rollout. The country began giving shots to everyone over the age of 16 in December.
"This clearly demonstrates the power of the COVID-19 vaccine to fight this virus and encourages us to continue even more intensively with our vaccination campaign," Israel Ministry of Health Director Yeheskel Levy said in a statement. "We aim to achieve even higher uptake in people of all ages, which gives us hope of regaining normal economic and social function in the not so distant future.”
The data were collected by Israel's Ministry of Health between January 17 and March 6, and compared the outcomes of people who had been vaccinated with those who had not.
The companies said unvaccinated individuals were 44 times more likely to develop symptomatic COVID-19, and 29 times more likely to die from COVID-19 than those who had received the vaccine.
At the time of the data collection, the Pfizer-BioNTech shot was the only vaccine available in the country and the more transmissible B.1.1.7 variant, the variant first found in the U.K., was the dominant strain. More than 80 percent of the tested specimens when the analysis was conducted were variant B.1.1.7, the companies said.