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Second Booster Vaccine Dose for Older Adults and COVID-19 Mortality During the Omicron Surge
23 Pages Posted: 25 Mar 2022More...
Background: The rapid emergence of the B.1.1.529 (omicron) variant of severe acute respiratory syndrome coronavirus-2 led to a global resurgence of coronavirus disease 2019 (Covid-19). On January 2nd, 2022, Israeli authorities approved a 4th Covid-19 vaccine dose (second-booster) for individuals aged 60 to 100 who received a first booster dose four or more months earlier. Evidence regarding the effectiveness of a second-booster dose in reducing mortality due to Covid-19 is warranted.
Methods: This retrospective cohort study included all members of Clalit Health Services, aged 60 or older, who received a BNT162b2 booster dose at least 4 months earlier. Mortality due to Covid-19 among participants who received the second-booster was compared with that among participants who received one booster dose. A Cox proportional-hazards regression model with time-dependent covariates was used to estimate the association between the second-booster and death due to Covid-19 while adjusting for demographic factors and coexisting illnesses.
Findings: A total of 563,465 participants met the eligibility criteria. Of those, 328,597 (58%) received a second-booster dose during the 40-day study period. Death due to Covid-19 occurred in 92 second-booster recipients and 232 participants who received just the first-booster dose. The adjusted hazard ratio for mortality was 0.22 (95% confidence interval, 0.17 to 0.28).
Interpretation: Participants who received a second-booster dose at least four months after a first BNT162b2 booster had 78% lower mortality due to Covid-19 than participants who received only the first booster during the omicron surge.
Funding Information: None.
Declaration of Interests: None.
Ethics Approval Statement: The study was approved by the CHS Community Helsinki Committee and the CHS Data Utilization Committee. The study was exempt from the requirement for informed consent from the patients, owing to the retrospective design.
Suggested Citation: Suggested Citation