Download This Paper
Preprints with The Lancet is a collaboration between The Lancet Group of journals and SSRN to facilitate the open sharing of preprints for early engagement, community comment, and collaboration. Preprints available here are not Lancet publications or necessarily under review with a Lancet journal. These preprints are early-stage research papers that have not been peer-reviewed. The usual SSRN checks and a Lancet-specific check for appropriateness and transparency have been applied. The findings should not be used for clinical or public health decision-making or presented without highlighting these facts. For more information, please see the FAQs.
Effectiveness of a Second COVID-19 Vaccine Booster on All-Cause Mortality in Long-Term Care Facility Residents and in the Oldest Old: A Nationwide, Retrospective Cohort Study in Sweden
22 Pages Posted: 12 May 2022
More...Abstract
Background: The effect of a second booster dose of COVID-19 vaccine on the risk of death from all causes among the oldest and frailest individuals is unknown. We aimed to investigate the relative vaccine effectiveness of a second booster dose against all-cause mortality in residents of long-term care facilities and in the oldest old.
Methods: Two nationwide matched cohorts were formed using Swedish nationwide registers. In the first, residents of LTCFs who were given a second booster with either BNT162b2 or mRNA-1273 from 1 January 2022 onwards were matched 1:1 exactly on birth year and county of residence to residents given only the first booster (N=25,252). In the second, all individuals living in Sweden aged >80 years who were given the second booster were matched 1:1 to individuals given the first booster (N=397,394). Baseline in each matched pair was the date of vaccination in second-booster recipients. The outcome was all-cause mortality until 29 March 2022.
Findings: From 7 days after baseline and onwards, there were 330 deaths in the LTCF cohort during a median follow-up of 21 days. Compared to the first booster, the second booster had an adjusted relative vaccine effectiveness of 31% (95% CI, 14-45). In the cohort of all individuals aged >80 years, there were 1025 deaths during a median follow-up of 20 days. The adjusted relative vaccine effectiveness of the second booster in this cohort was 42% (95% CI, 35-49), with greater effectiveness (P=0·004 for interaction) when compared to first-booster recipients in which more than 4 months had passed since vaccination (52%, 95% CI, 42-61).
Interpretation: As compared with a first booster, a second booster dose with either BNT162b2 or mRNA-1273 was associated with reduced short-term risk of death from all causes among residents in LTCFs and in the oldest old during the Omicron era. These findings suggest that promoting a high uptake of booster doses in old and frail people may prevent premature deaths.
Funding: There was no funding source for this study.
Declaration of Interest: We declare no competing interests.
Ethical Approval: The study was approved by the Swedish Ethical Review Authority (no. 2021-00094) who waived the informed consent requirement given the retrospective design
Note: Published: July 13, 2022 THE LANCET, Regional Health, Europe. https://doi.org/10.1016/j.lanepe.2022.100466
Suggested Citation: Suggested Citation