Pfizer-BioNTech COVID-19 Vaccine Found Effective in Large, “Real World” Study

Results of a new study show that the Pfizer-BioNTech COVID-19 vaccine is 92% effective at preventing severe COVID-19 after 2 doses in over half a million study participants.

A “real world” test of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccine in over half a million people in Israel confirmed its efficacy in preventing serious illness and death, even after 1 dose.

The study results—published February 24, 2021 in The New England Journal of Medicine—offer reassurance that the vaccine’s benefits seen in smaller testing can persist when used in a general population with various ages and health conditions.

The study was conducted by researchers from the Clalit Research Institute and Ben-Gurion University of the Negev, both in Israel, as well as Harvard University in the US.

Researchers used data from Israel’s largest health care organization to evaluate the effectiveness of the vaccine, instead of efficacy and safety, but no unexpected issues arose in previous studies, noted study authors.

Researchers compared 596 618 persons aged ≥16 years who were newly vaccinated between December 20, 2020 and February 1, 2021 to an equal number of participants of similar age, sex, and health who did not receive the vaccine. All the participants had not previously tested positive for COVID-19.

The results showed that the vaccine was 92% effective at preventing severe COVID-19 after 2 doses and 62% effective after 1 dose. The vaccine was about 72% effective in preventing mortality 2-3 weeks after the first dose.

Also, the estimated vaccine efficacy against COVID-19 symptoms was 57% 2-3 weeks after the first dose, and 94% ≥7 days after the second dose. When looking at COVID-19-related hospitalization, the vaccine was 74% effective at preventing hospitalization after 1 dose and 87% after 2 doses.

The study also shows that the vaccine was 46% effective at preventing confirmed infection after 1 dose and 92% effective after 2 doses. There was a total of 41 COVID-19-related deaths, 32 of them in people who did not receive the vaccine.

In addition, the researchers noted that the vaccine effectiveness was similar for participants aged ≥70 years and for the younger participants.

“These results strengthen the expectation that newly approved vaccines can help to mitigate the profound global effects of the Covid-19 [sic] pandemic,” concluded study authors.


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