Abstract
Background: The emergence of the B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 and the reduced effectiveness over time of the BNT162b2 vaccine (Pfizer-BioNTech) led to a resurgence of coronavirus disease 2019 (Covid-19) cases in populations that had been vaccinated early. On July 30, 2021, the Israeli Ministry of Health approved the use of a third dose of BNT162b2 (booster) to cope with this resurgence. Evidence regarding the effectiveness of the booster in lowering mortality due to Covid-19 is still needed.
Methods: We obtained data for all members of Clalit Health Services who were 50 years of age or older at the start of the study and had received two doses of BNT162b2 at least 5 months earlier. The mortality due to Covid-19 among participants who received the booster during the study period (booster group) was compared with that among participants who did not receive the booster (nonbooster group). A Cox proportional-hazards regression model with time-dependent covariates was used to estimate the association of booster status with death due to Covid-19, with adjustment for sociodemographic factors and coexisting conditions.
Results: A total of 843,208 participants met the eligibility criteria, of whom 758,118 (90%) received the booster during the 54-day study period. Death due to Covid-19 occurred in 65 participants in the booster group (0.16 per 100,000 persons per day) and in 137 participants in the nonbooster group (2.98 per 100,000 persons per day). The adjusted hazard ratio for death due to Covid-19 in the booster group, as compared with the nonbooster group, was 0.10 (95% confidence interval, 0.07 to 0.14; P<0.001).
Conclusions: Participants who received a booster at least 5 months after a second dose of BNT162b2 had 90% lower mortality due to Covid-19 than participants who did not receive a booster.
【초록키워드】 coronavirus disease, Coronavirus disease 2019, BNT162b2 vaccine, coronavirus, Mortality, variant, B.1.617.2, severe acute respiratory syndrome Coronavirus, Population, BNT162b2, Regression model, Effectiveness, death, age, eligibility criteria, Pfizer-BioNTech, booster, association, dose, acute respiratory syndrome, Older, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, 95% confidence interval, adjusted hazard ratio, second dose, study period, participant, covariate, lower mortality, sociodemographic factors, resurgence, service, Sociodemographic factor, Ministry of Health, was used, occurred, approved, reduced, per day, conditions, receive, of BNT162b2,