Top 5 Takeaways

1. Effectiveness of Monovalent mRNA Vaccines: During the SARS-CoV-2 Omicron BA.1/BA.2 and BA.4/BA.5 periods, the effectiveness of three-dose monovalent mRNA vaccines against COVID-19–associated hospitalization waned over time.
2. Vaccine Effectiveness Decrease: The study observed a decrease in effectiveness from 79% to 60% in the initial 120 days after the third dose, dropping further to 41% and 29%, respectively, after 120 days.
3. Public Health Implication: This indicates the need for updated bivalent COVID-19 mRNA vaccines, especially to maximize protection against newer BA.4/BA.5 lineages and prevent COVID-19–associated hospitalization.
4. Waning Protection: Vaccine-induced immunity wanes over time, more notably in the BA.4/BA.5 period, highlighting the importance of booster doses.
5. Study Period and Methodology: The study was conducted from December 26, 2021, to August 31, 2022, across 18 states, utilizing a test-negative, case-control analysis within the IVY Network.

Original Article Author and Citation

Corresponding Author

Diya Surie, dsurie@cdc.gov

Suggested Citation

Surie D, Bonnell L, Adams K, et al. Effectiveness of Monovalent mRNA Vaccines Against COVID-19–Associated Hospitalization Among Immunocompetent Adults During BA.1/BA.2 and BA.4/BA.5 Predominant Periods of SARS-CoV-2 Omicron Variant in the United States — IVY Network, 18 States, December 26, 2021–August 31, 2022. MMWR Morb Mortal Wkly Rep 2022;71:1327–1334. DOI: http://dx.doi.org/10.15585/mmwr.mm7142a3 .

Summary

The study investigated the effectiveness of monovalent mRNA COVID-19 vaccines against hospitalization during the BA.1/BA.2 and BA.4/BA.5 periods. It found that vaccine effectiveness wanes significantly over time.

Methods

The research was conducted as a test-negative, case-control analysis within the IVY Network, involving adults aged ≥18 years. It compared vaccinated and unvaccinated groups for COVID-19–associated hospitalization.

Discussion

The findings highlight the diminishing effectiveness of the monovalent mRNA vaccines over time, especially during the BA.4/BA.5 period. This decrease underlines the necessity of updated booster vaccines.

Conclusion

The study concludes that the effectiveness of monovalent mRNA COVID-19 vaccines against hospitalization wanes over time, emphasizing the importance of updated bivalent boosters for better protection against emerging SARS-CoV-2 lineages.

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