High Efficacy of Pfizer COVID-19 Vaccine in a Nationwide Mass Vaccination Program

In a nationwide mass vaccination campaign, the BNT162b2 mRNA vaccine from Pfizer-BioNTech was found to be effective at preventing a wide range of COVID-19-related outcomes. These findings were published in The New England Journal of Medicine.

Data from Clalit Health Services, which covers 53% of the population in Israel, were analyzed for this study. Vaccinated individuals (n=596,618) aged greater than 16 years who had not tested positive for SARS-CoV-2 were matched by age, gender, and geographical location in a 1:1 ratio with an unvaccinated individual. Study outcomes included documented infection with SARS-CoV-2, symptomatic COVID-19, COVID-19-related hospitalization, severe illness, and death.

The study population were aged median 45 years (interquartile range [IQR], 35-62), 50% were men, and 56.7% had no COVID-19 risk criteria.

At day 15 after vaccination, 10,561 (0.6 per 1000 person-days) COVID-19 infections were documented. Among the infections, 5995 were symptomatic, 369 patients were admitted to the hospital, and 41 died.

Between days 14 and 20, data shows the vaccine was effective at:

• Preventing documented infection with SARS-CoV-2: 46% (95% CI, 40%-51%)
• Preventing symptomatic COVID-19 infection: 57% (95% CI, 50-63%)
• Preventing COVID-19-related hospitalization: 75% (95% CI, 56-86%)
• Preventing severe illness: 62% (95% CI, 39-80%)
• Preventing COVID-19-related mortality: 72% (95% CI, 19-100%)

Following the second dose, the vaccine was observed to be 92% effective (95% CI, 88%-95%) at preventing documented infection.

After 2 doses, the vaccine was estimated to be at least 90% effective at preventing documented infection among all subgroups, except individuals with at least 3 coexisting conditions (86%; 95% CI, 72%-95%). Similarly, the vaccine was estimated to be at least 90% effective at preventing symptomatic infection among all subgroups except among individuals with at least 3 coexisting conditions (89%; 95% CI, 68%-98%) and men (88%; 95% CI, 71%-98%).

Vaccination was estimated to be effective at 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 included some selection bias, because it was difficult to match older individuals with an unvaccinated comparator, so were removed from the study.

These data indicated the BNT162b2 vaccine was highly efficacious at preventing COVID-19-related outcomes in a real-world vaccination program.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Dagan N, Barda N, Kepten E, et al. BNT162b2 mRNA COVID-19 vaccine in a nationwide mass vaccination setting. N Engl J Med. Published online February 24, 2021. doi:10.1056/NEJMoa2101765.

This article originally appeared on Infectious Disease Advisor