J Korean Med Sci.  2024 Sep;39(37):e258. 10.3346/jkms.2024.39.e258.

Effectiveness of the Bivalent mRNA COVID-19 Vaccine for Preventing Critical Infection From the SARS-CoV-2 Omicron Variant in the Republic of Korea

• Choi YS
• Ryu S
• Kim RK
• Chiara A
• Baek S
• Nam H
• Park E
• Kim EK
• Choe YJ
• Kwon D
• Choi WS

• KMID: 2559780
• DOI: http://doi.org/10.3346/jkms.2024.39.e258

Abstract

Background
This retrospective observational matched cohort study assessed the differences in critical infections caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) during the omicron-predominant period of the coronavirus disease 2019 (COVID-19) pandemic. We evaluated the vaccine effectiveness of bivalent mRNA vaccine compared to unvaccinated individuals.
Methods
We collected COVID-19 case data from the Korean COVID-19 vaccine effectiveness cohort. We calculated the probability of critical COVID-19 cases by comparing the vaccinated and unvaccinated groups.
Results
The risk of being critically infected due to SAR-CoV-2 infection was 5.96 times higher (95% confidence interval, 5.63–6.38) among older individuals who were unvaccinated compared to those who received the bivalent COVID-19 vaccine.
Conclusion
Our findings indicate that the bivalent vaccine reduces the disease burden of the SARS-CoV-2 omicron variant, particularly among the older population. Further studies are warranted to determine the effectiveness of booster doses of vaccines for SARS-CoV-2 infection.

Keyword

SARS-CoV-2; Vaccine, Bivalent; COVID-19; Older People; Vaccine Effectiveness

Figure

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  Fig. 1 Probability of critical infection and bivalent COVID-19 vaccine effectiveness against severe SARS-CoV-2 infection and death in the Republic of Korea. (A) Proportion of individuals critical infection due to SARS-CoV-2 during the omicron wave of the COVID-19 pandemic by demographic characteristic, including sex, age, and history of SARS-CoV-2 infection. (B) Vaccine effectiveness against critical infection due to SARS-CoV-2 compared to those who did not receive the COVID-19 vaccine. The points are mean estimates, and the vertical bars indicate 95% confidence intervals.SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2, COVID-19 = coronavirus disease 2019.

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