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Long-Term Effectiveness of COVID-19 Vaccines Against Infections, Hospitalizations, and Mortality in Adults: Findings from a Rapid Living Systematic Evidence Synthesis and Meta-Analysis Up to August 2022
25 Pages Posted: 26 Sep 2022
More...Abstract
Background: Synthesizing evidence on the long-term vaccine effectiveness (VE) of COVID-19 vaccines (BNT162b2, mRNA-1273, ChAdOx1/AZD1222, and Ad26.COV2.S) against infections, hospitalizations, and mortality is crucial to making evidence-based pandemic policy decisions.
Methods: We searched EMBASE and the iSearch COVID-19 Portfolio, supplemented by hand searching, until August 11, 2022 for studies that reported VE immediate and 112+ days after a primary vaccine series or 84+ days after a booster dose. Single reviewers evaluated titles, abstracts, and full-text articles, and extracted data, with a second reviewer verifying included studies. Three-level meta-analytic models assessed VE against COVID-19 infections, hospitalizations, and mortality.
Findings: This review included 55 studies. For infections caused by any SARS-CoV-2 strain, VE for the primary series fell from 83% [CI: 80 to 86] at baseline to 62% [CI: 52 to 70] by 112+ days. For hospitalizations and mortality, VE at baseline was 91% [CI: 88 to 93] and 91% [CI: 85 to 95], respectively, and declined to 76% [CI: 57 to 87] at 224-251 days and 81% [CI: 66 to 90] at 140-167 days. The patterns of VE estimates were lower for the Omicron variant, but the long-term patterns were similar compared to all strains. VE estimates for booster doses against infections and hospitalizations, which covered mostly Omicron studies, were 69% [CI: 51 to 80] and 87% [CI: 81 to 91] at baseline, respectively, and declined to 55% [CI: 25 to 72] and 65% [CI: 45 to 78], respectively, at 112+ days.
Interpretation: Our analyses indicate that VE generally decreases against COVID-19 infections, hospitalizations, and mortality. The baseline VE levels for the Omicron variant were notably lower than for other variants. Therefore, other preventive measures (e.g., mask-wearing and physical distancing) may be necessary to manage the pandemic in the long term.
Funding Information: The development and continued updating of this living evidence synthesis has been funded by the Canadian Institutes of Health Research (CIHR) and the Public Health Agency of Canada (PHAC), through the COVID-19 Evidence Network to support Decision-making (COVID-END) network.
Declaration of Interests: In the last 3 years, Dr. Bacon has received consultancy and speaker fees from Resplipus, an investigator-generated educational grant from Moderna, and has served on advisory boards for Bayer, Sanofi, Respiplus, and Sojecci Inc., none of which are related to the current article. The other authors have no conflicts of interest to declare.
Keywords: effectiveness, COVID-19 vaccines, infections, hospitalizations, and mortality
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