In a new study, researchers found that the Pfizer COVID-19 vaccine is 94% effective.
They tested 1.2 million people in Israel.
The researchers also found there may be a strong protective benefit against infection, a crucial element in breaking onward transmission.
This is the first real-world study confirming the power of mass immunization campaigns to fight COVID-19.
The research was conducted by a team at the Clalit Research Institute and elsewhere.
In the study, the team tested around 1.2 million people who were divided into equal groups of vaccinated and unvaccinated.
Each vaccinated participant was matched to an unvaccinated “control” person of similar age, sex, geographic, medical and other characteristics.
The researchers then recorded outcomes at days 14-20 after the first of the two doses and day seven or more after the second.
The experiment was carried out between December 20 2020 and February 1, 2021.
The team found the efficacy against symptomatic infections was 57% between 14-20 days after the first dose, but rose to 94% seven days after the second dose—very close to the 95% achieved during Phase 3 clinical trials.
People who received second doses were also highly protected against hospitalization and death—though the precise numbers here are less significant.
The team also found people who received their second dose had a 92% lower chance of getting any form of infection at all compared to those who were unvaccinated.
Researchers say the findings were considered encouraging, but more confirming evidence is needed in the future.
One author of the study is Noam Barda.
The study is published in the New England Journal of Medicine.
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