Pfizer and BioNTech's Covid-19 vaccine showed 94 per cent efficacy in a real world study conducted in Israel involving 1.2 million people.
The findings published in the New England Journal of Medicine showed that the vaccine performed as well as it did in the clinical trials.
In this study, all persons who were newly vaccinated during the period from December 20, 2020, to February 1, 2021, were matched to unvaccinated controls in a 1:1 ratio according to demographic and clinical characteristics. Each study group included 596,618 persons.
Study outcomes included documented infection with SARS-CoV-2, symptomatic Covid-19, Covid-19-related hospitalisation, severe illness, and death.
The researchers analysed data from Clalit Health Services (CHS), the largest of four integrated health care organisations in Israel.
That a vaccine will perform as well in the real world as it does in the highly controlled setting of a clinical trial is not a given, noted senior author Ran Balicer, Director of the Clalit Research Institute of Israel, health news site STAT reported on Wednesday.
Estimated vaccine effectiveness during the follow-up period starting seven days after the second dose was 92 per cent for documented infection, 94 per cent for symptomatic Covid-19, 87 per cent for hospitalisation, and 92 per cent for severe Covid-19, said the study.
Effective in all age groups
The researchers estimated that the vaccine effectiveness was similar for adults 70 years of age or older and for younger age groups for the same time period.
"This study estimates a high effectiveness of the BNT162b2 vaccine for preventing symptomatic Covid-19 in a noncontrolled setting, similar to the vaccine efficacy reported in the randomized trial," wrote the researchers.
"Our study also suggests that effectiveness is high for the more serious outcomes: hospitalisation, severe illness, and death."