J Korean Med Sci.  2023 Nov;38(46):e396. 10.3346/jkms.2023.38.e396.

Comparative Effectiveness of COVID-19 Bivalent Versus Monovalent mRNA Vaccines in the Early Stage of Bivalent Vaccination in Korea: October 2022 to January 2023

• Kim RK
• Choe YJ
• Jang EJ
• Chae C
• Hwang JH
• Lee KH
• Shim JA
• Kwon GY
• Lee JY
• Park YJ
• Lee SW
• Kwon D

• KMID: 2548545
• DOI: http://doi.org/10.3346/jkms.2023.38.e396

Abstract

Background
This retrospective observational matched-cohort study of 2,151,216 individuals from the Korean coronavirus disease 2019 (COVID-19) vaccine effectiveness cohort aimed to evaluate the comparative effectiveness of the COVID-19 bivalent versus monovalent vaccines in providing additional protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, critical infection, and death in Korea.
Methods
Among individuals, those vaccinated with COVID-19 bivalent vaccines were matched in a 1:1 ratio with those who were vaccinated with monovalent vaccines (bivalent vaccines non-recipients) during the observation period. We fitted a time-dependent Cox proportional-hazards model to estimate hazard ratios (HRs) of COVID-19 outcomes for infection, critical infection, and death, and we defined vaccine effectiveness (VE) as 1–HR.
Results
Compared with the bivalent vaccination group, the incidence proportions in the monovalent vaccination group were approximately three times higher for infection, nine times higher for critical infection, and 11 times higher for death. In the early stage of bivalent vaccination, relative VE of bivalent vaccine against monovalent vaccine was 42.4% against SARS-CoV-2 infection, 81.3% against critical infection, and 85.3% against death. In addition, VE against critical infection and death according to the elapsed period after bivalent vaccination was maintained at > 70%.
Conclusion
The bivalent booster dose provided additional protection against SARS-CoV-2 infections, critical infections, and deaths during the omicron variant phase of the COVID-19 pandemic.

Keyword

Bivalent Vaccine; COVID-19; SARS-CoV-2; Vaccine Effectiveness

Figure

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  Fig. 1 Definitions of the study population for the comparative effectiveness of the COVID-19 bivalent vaccine.K-COVE = Korean COVID-19 Vaccine Effectiveness, COVID-19 = coronavirus disease 2019.

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  Fig. 2 Time-varying COVID-19 VE against infection, critical infection, and death in individuals who received bivalent vaccine compared with those who received monovalent vaccine. Error bars indicate 95% CIs.VE = vaccine effectiveness, COVID-19 = coronavirus disease 2019, CI = confidence interval.

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