In a nationwide mass vaccination campaign, Pfizer-BioNTech’s BNT162b2 mRNA vaccine was found to be effective in preventing a wide variety of COVID-19-related outcomes. These results were published in the New England Journal of Medicine.
For this study, data from Clalit Health Services covering 53% of the population in Israel were analyzed. Vaccinated persons (n = 596,618) over the age of 16 who had not tested positive for SARS-CoV-2 were compared in a ratio of 1: 1 with a non-vaccinated person according to age, gender and geographic location. Study results included documented SARS-CoV-2 infections, symptomatic COVID-19, COVID-19-related hospitalizations, serious illness and death.
The study population was on average 45 years old (interquartile range) [IQR], 35-62), 50% were men and 56.7% had no COVID-19 risk criteria.
On day 15 after vaccination, 10,561 (0.6 per 1000 person-days) COVID-19 infections were documented. Among the infections, 5,995 were symptomatic, 369 patients were hospitalized and 41 died.
Between days 14 and 20, the data shows the vaccine was effective on:
- Prevention of documented infection with SARS-CoV-2: 46% (95% CI, 40% -51%)
- Prevention of symptomatic COVID-19 infection: 57% (95% CI, 50-63%)
- Prevention of COVID-19-related hospital stays: 75% (95% CI, 56-86%)
- Major Disease Prevention: 62% (95% CI, 39-80%)
- Prevention of COVID-19-related mortality: 72% (95% CI, 19-100%)
After the second dose, the vaccine was observed to be 92% effective (95% CI, 88% -95%) in preventing documented infection.
After 2 doses, the vaccine was estimated to be at least 90% effective in preventing documented infection in all subgroups, with the exception of those with at least 3 concurrent conditions (86%; 95% CI, 72% -95%). Similarly, the vaccine was estimated to be at least 90% effective in preventing symptomatic infection in all subgroups, with the exception of those with at least 3 concurrent conditions (89%; 95% CI, 68% -98%) and men (88%; 95% CI, 71% -98%).
It was estimated that vaccination was effective in preventing asymptomatic infection by 29% (95% CI, 17% -39%) after the first dose and 90% (95% CI, 83% -94%) after the second.
This study may have contained some selection bias as it was difficult to compare older people with an unvaccinated comparator, so they were removed from the study.
These data showed that the BNT162b2 vaccine was highly effective in preventing COVID-19-related outcomes in a real-life vaccination program.
Disclosure: Several authors have declared their affiliations with the industry. For a full list of details, see the original article.
Dagan N., Barda N., Kepten E. et al. BNT162b2 mRNA COVID-19 vaccine in a statewide mass vaccination environment. N Engl J Med. Published online February 24, 2021. doi: 10.1056 / NEJMoa2101765.
This article originally appeared on Infectious Disease Advisor