Systematic review and meta-analysis of COVID-19 mRNA vaccine effectiveness against hospitalizations in adults.

Background: During the coronavirus disease 2019 (COVID-19) pandemic, Pfizer/BioNTech BNT162b2, and Moderna mRNA-1273 vaccines were central to the global pandemic control measures. Methods: Here, we conducted a systematic review and meta-analysis to evaluate their real-world vaccine effectiveness (VE). Our study focussed on those that reported the efficacy of these vaccines against COVID-19 hospitalization. Hospitalization was chosen as the primary outcome as it directly reflects the ability of the vaccine to prevent severe disease. A literature search was undertaken using Medline and Embase on 25 February 2024. From this, 50 studies out of 18,347 articles were included for further analysis. Results: High VE against hospitalization was reported for both the BNT162b2 and mRNA-1273 COVID-19 vaccines when used either as a primary vaccination series (2-dose) or following an additional booster dose (3-dose). Meta-analysis indicated that the pooled VE estimates for each of these vaccination protocols ranged from 84% to 86%, suggesting strong protectiveness. Our data also imply that booster doses can restore waning effectiveness, with no significant differences observed in VE between the 2-dose and 3-dose protocols. However, subgroup analysis revealed an association between the presence of the Omicron variant and a drop in VE, indicating that future emerging SARS-CoV-2 virus variants could similarly affect VE. Conclusions: Our review underscores the importance of ongoing research to ensure vaccine strategies remain effective against evolving variants. Our study also identified the need for expanding data collection to include underrepresented populations.