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Objectives@#We evaluated the effectiveness of coronavirus disease 2019 vaccination in high-risk facilities in the Republic of Korea during the period when the highly transmissible Delta variant was prevalent. Additionally, we aimed to explore any disparities in vaccine effectiveness (VE) across various types of institutions, specifically distinguishing between non-medical and medical establishments. @*Methods@#We examined 8 outbreak clusters covering 243 cases and 895 contacts from 8 highrisk facilities divided into 2 groups: group A (4 non-medical institutions) and group B (4 medical institutions). These clusters were observed from July 27, 2021 to October 16, 2021 for the attack rate (AR) and VE with respect to disease severity. A generalized linear model with a binomial distribution was used to determine the odds ratio (OR) for disease severity and death. @*Results@#AR was notably lower in group B (medical institutions). Furthermore, VE analysis revealed that group A exhibited higher effectivity for disease severity and death than group B. The OR for disease severity was 0.24 (95% confidence interval [CI], 0.03–2.16) for group A and 0.27 (95% CI, 0.12–0.64) for group B, with the OR for death at 0.12 (95% CI, 0.01–1.32) in group A and 0.34 (95% CI, 0.14–0.87) in group B. @*Conclusion@#Although VE may vary across institutions, our findings underscore the importance of implementing vaccinations in high-risk facilities. Customized vaccination programs, tailored response plans, and competent management personnel are essential for effectively addressing and mitigating public health challenges.
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Objectives@#The Korea Disease Control and Prevention Agency promotes vaccination by regularly providing information on its benefits for reducing the severity of coronavirus disease 2019 (COVID-19). This study aimed to analyze the number of averted severe COVID-19 cases and COVID-19-related deaths by age group and quantify the impact of Republic of Korea’s nationwide vaccination campaign. @*Methods@#We analyzed an integrated database from the beginning of the vaccination campaign on February 26, 2021 to October 15, 2022. We estimated the cumulative number of severe cases and COVID-19-related deaths over time by comparing observed and estimated cases among unvaccinated and vaccinated groups using statistical modeling. We compared daily age-adjusted rates of severe cases and deaths in the unvaccinated group to those in the vaccinated group and calculated the susceptible population and proportion of vaccinated people by age. @*Results@#There were 23,793 severe cases and 25,441 deaths related to COVID-19. We estimated that 119,579 (95% confidence interval [CI], 118,901–120,257) severe COVID-19 cases and 137,636 (95% CI, 136,909–138,363) COVID-19-related deaths would have occurred if vaccination had not been performed. Therefore, 95,786 (95% CI, 94,659–96,913) severe cases and 112,195 (95% CI, 110,870–113,520) deaths were prevented as a result of the vaccination campaign. @*Conclusion@#We found that, if the nationwide COVID-19 vaccination campaign had not been implemented, the number of severe cases and deaths would have been at least 4 times higher. These findings suggest that Republic of Korea’s nationwide vaccination campaign reduced the number of severe cases and COVID-19 deaths.
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Background@#This study aimed to investigate the deaths due to coronavirus disease 2019 (COVID-19) reinfection and related risk factors. @*Methods@#National cohort data were collected for a six-month period when omicron BA.1/BA.2 variant was dominant in South Korea. @*Results@#The long-term care facility residents (adjusted odds ratio, 3.11; 95% confidence interval [CI], 2.98–3.25) had significantly higher risk of reinfection than the general population. The risk of reinfection was significantly lower for persons with 2 or more vaccine doses compared to the unvaccinated. The risk of death was significantly higher in the reinfection group than in the primary infection group for persons in the 60–74 years age group (adjusted relative risk [aRR], 1.62; 95% CI, 1.19–2.20), and immunocompromised group (aRR, 4.56; 95% CI, 2.34–8.90). @*Conclusion@#In these data, vaccination history was significantly related to reduced COVID-19 reinfection and severe progression, and scheduled vaccinations were important even with a history of infection.
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We conducted a cohort study to assess vaccine effectiveness (VE) of coronavirus disease 2019 vaccine combinations on severe acute respirator y syndrome coronavirus 2 critical infection and death among elderly population in Korea. From Januar y to August 2022, VE against death for 4 doses mRNA recipients was 96.1%, whereas 1-dose viral vector + 3-dose mRNA recipients had VE of 90.8%.