The study found that people who received their second dose of the vaccine were 92% less likely to get some form of infection compared to those who were not vaccinated.
Pfizer’s COVID-19 vaccine was found to be 94% effective in a study of 1.2 million people in Israel, the first real-world, peer-reviewed research confirming the power of mass vaccination campaigns to put end to the pandemic.
The article, which appeared in the New England Journal of Medicine on Wednesday, also demonstrated that there is likely a strong protective benefit against infection, which is crucial in interrupting transmission.
“The fact that vaccines have worked so well in the real world … really suggests that if the nations of the world can find the will, we now have the means to end COVID-19 forever,” Ben Neuman said. , virologist. from Texas A&M University which was not involved in the research.
The experiment was conducted between December 20, 2020 and February 1, 2021 – a time when a new variant first identified in Britain was endemic in Israel, making the vaccine’s performance all the more impressive.
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About 1.2 million people were divided into equal groups of vaccinated and unvaccinated.
Each vaccinated participant was matched with an unvaccinated “control” person with similar age, gender, geographic, medical, and other characteristics.
Lead author Noam Barda, head of epidemiology and research at the Clalit Research Institute, told AFP that the pairing process was very robust.
An elderly ultra-Orthodox Jewish man from a particular neighborhood with a particular set of comorbidities and a history of influenza vaccination would be matched with someone else matching that specific profile, for example.
The researchers then recorded the results on days 14-20 after the first of two doses and seven or more days after the second.
Efficacy against symptomatic infections was 57% between 14 and 20 days after the first dose, but increased to 94% within seven days after the second dose – very close to the 95% achieved in phase III clinical trials.
People who received a second dose were also highly protected against hospitalization and death – although the precise numbers here are less significant and have a wider statistical range due to the relatively lower number of cases.
The study also found that people who received their second dose were 92% less likely to get some form of infection compared to those who were not vaccinated.
While the finding was deemed encouraging, researchers and outside experts said it needed more substantiated evidence.
This is because the participants were not systematically tested at regular intervals; instead, they were given a test when they wanted one.
The authors have attempted to correct this with statistical methods, but the result is probably still imperfect.
“Unless you test everyone all the time, this will miss some infections,” said Natalie Dean, a biostatistician at the University of Florida.
She added that she was certain there was a strong protective benefit, but “nailing that number more precisely will require specialist study designs with frequent testing.”