J Korean Med Sci.  2022 Sep;37(35):e267. 10.3346/jkms.2022.37.e267.

Relative Effectiveness of COVID-19 Vaccination in Healthcare Workers: 3-Dose Versus 2-Dose Vaccination

• Kim SR
• Kang HJ
• Jeong HR
• Jang SY
• Lee JE
• Kim DE
• Lee HR
• Cho MH
• Noh JY
• Cheong HJ
• Kim WJ
• Song JY

• KMID: 2532921
• DOI: http://doi.org/10.3346/jkms.2022.37.e267

Abstract

The omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to have high infectivity and is more likely to evade vaccine immunity. However, booster vaccination is expected to strengthen cross-reactive immunity, thereby increasing the vaccine effectiveness (VE). This study aimed to evaluate the relative VE of the 3-dose (booster) vaccination compared with the 2-dose primary series vaccination in healthcare workers during omicron variant-dominant periods. During the omicron-dominant period from February 1, 2022 to February 28, 2022, a 1:1 matched case-control study was conducted. Healthcare workers with positive SARS-CoV-2 test results were classified as positive cases, whereas those with negative results served as controls. Compared with the 2-dose primary series vaccination, booster vaccination with mRNA vaccine showed moderate VE (53.1%). However, in multivariate analysis including the time elapsed after vaccination, the significant VE disappeared, reflecting the impact of recent vaccination rather than the third dose itself.

Keyword

SARS-CoV-2; COVID-19; Healthcare Worker; Vaccine Effectiveness

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