Top 5 Takeaways

1. Effectiveness of Bivalent Booster: The study found an 84% effectiveness of the bivalent booster against COVID-19 hospitalization compared to unvaccinated individuals.
2. Relative Vaccine Effectiveness: Compared to those who received ≥2 monovalent-only mRNA vaccine doses, the bivalent booster showed a relative effectiveness of 73%.
3. Study Population and Methodology: The study involved 1,168 immunocompetent adults aged ≥65 years, part of the IVY Network, across 18 states, with a case-control analysis.
4. Additional Benefits of the Bivalent Booster: The booster provided significant additional protection against COVID-19 hospitalization, especially in adults aged ≥65 years with underlying conditions.
5. Limitations and Future Directions: The study acknowledges limitations like insufficient sample size for certain analyses and the need for ongoing monitoring amidst emerging variants.

Original Article Author and Citation

Corresponding Author

Diya Surie,

Suggested Citation

Surie D, DeCuir J, Zhu Y, et al. Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–Associated Hospitalization Among Immunocompetent Adults Aged ≥65 Years — IVY Network, 18 States, September 8–November 30, 2022. MMWR Morb Mortal Wkly Rep 2022;71:1625–1630. DOI:


The study focused on the effectiveness of a bivalent mRNA booster in preventing COVID-19 hospitalization among adults aged ≥65. It utilized a test-negative design, case-control analysis, including patients from 22 hospitals in the IVY Network. The booster showed strong protective effects against COVID-19 hospitalization, especially compared to unvaccinated individuals and those with prior monovalent-only mRNA vaccinations.


The research involved immunocompetent adults aged ≥65 years, admitted for COVID-19-like illness. Data were collected through EMR review and interviews, and COVID-19 status was verified using various testing methods. The analysis was stratified based on the vaccination status and the interval between the last monovalent vaccine dose and illness onset.


The bivalent booster offered substantial protection against COVID-19 hospitalization, particularly for older adults with comorbid conditions. This adds to the evidence supporting the use of bivalent mRNA boosters. The study also discussed comparisons with other international findings and the potential for bivalent boosters to adapt to evolving SARS-CoV-2 variants.


This study underscores the importance of the bivalent booster for older adults, particularly in the context of high COVID-19 community levels. It calls for increased coverage of bivalent boosters among eligible U.S. adults to prevent hospitalizations and recommends additional preventive strategies like indoor masking.


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