Effectiveness of SARS-CoV-2 Vaccines against Omicron Infection and Severe Events: A Systematic Review and Meta-Analysis of Test-Negative Design Studies

Abstract

AbstractBackgroundEvaluating vaccine effectiveness (VE) of a full vaccine series and booster doses against COVID-19 is important for health decision-making.MethodsWe systematically searched papers that evaluated VE of SARS-CoV-2 vaccines on PubMed, Web of Science, Cochrane Library, Google Scholar, Embase, Scopus, and preprint servers (bioRxiv and medRxiv) published from November 26th, 2021 to June 27th, 2022 (for full doses and first booster), and to January 8th, 2023 (for the second booster). The pooled VE against Omicron-associated symptomatic or any infection as well as severe events are estimated in a meta-analysis framework.ResultsFrom 2,552 citations identified, a total of 42 were included. The vaccination of the first booster provided stronger protection against Omicron than the full doses alone, shown by the VE estimates of 53.1% (95% CI: 48.0−57.8) vs. 28.6% (95% CI: 18.5−37.4) against infection and 82.5% (95% CI: 77.8−86.2) vs. 57.3% (95% CI: 48.5−64.7) against severe disease. The second booster offered strong protection among adults within 60 days of vaccination against infection (VE=53.1%, 95% CI: 48.0−57.8) and severe disease (VE=87.3% (95% CI: 75.5-93.4), comparable to the first booster with corresponding VE estimates of 59.9% against infection and 84.8% against severe disease. The VEs of the booster doses against severe disease among adults sustained beyond 60 days, 77.6% (95% CI: 69.4−83.6) for the first and 85.9% (95% CI: 80.3−89.9) for the second booster. The VE against infection was less sustainable regardless of dose type. Pure mRNA vaccines provided comparable protection to partial mRNA vaccines, but both provided higher protection than non-mRNA vaccination.ConclusionOne or two booster doses of current SARS-CoV-2 vaccines provide considerable protection against Omicron infection and substantial and sustainable protection against Omicron-induced severe clinical outcomes.FundingUS CDC U01 CK000670