Osong Public Health and Research Perspectives

Original Articles

Evaluation of COVID-19 vaccine effectiveness in different high-risk facility types during a period of Delta variant dominance in the Republic of Korea: a cross-sectional study: Min Jei Lee, Myung-Jae Hwang, Dong Seob Kim, Seon Kyeong Park, Jihyun Choi, Ji Joo Lee, Jong Mu Kim, Young-Man Kim, Young-Joon Park, Jin Gwack, Sang-Eun Lee; Osong Public Health Res Perspect. 2023;14(5):418-426. Published online October 19, 2023; DOI: https://doi.org/10.24171/j.phrp.2023.0188

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Graphical Abstract Abstract PDF: 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 high-risk 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.

Vaccine effectiveness and the epidemiological characteristics of a COVID-19 outbreak in a tertiary hospital in Republic of Korea: Seonhee Ahn, Tae Jong Son, Yoonsuk Jang, Jihyun Choi, Young Joon Park, Jiseon Seong, Hyun Hee Kwon, Muk Ju Kim, Donghyok Kwon; Osong Public Health Res Perspect. 2023;14(3):188-196. Published online June 8, 2023; DOI: https://doi.org/10.24171/j.phrp.2023.0066

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Graphical Abstract Abstract PDF: Objectives
Healthcare facilities are high-risk sites for infection. This study analyzed the epidemiological characteristics of a coronavirus disease 2019 (COVID-19) outbreak in a tertiary hospital after COVID-19 vaccination had been introduced in Republic of Korea. Vaccine effectiveness (VE) and shared anti-infection strategies are also assessed.
Methods
The risk levels for 4,074 contacts were evaluated. The epidemiological characteristics of confirmed cases were evaluated using the chi-square test. The “1 minus relative risk” method was used to determine VE in preventing infection, progression to severe disease, and death. In the largest affected area (the 8th floor), a separate relative risk analysis was conducted. A multivariate logistic regression analysis (with 95% confidence interval [CIs]) was used to identify transmission risk factors with a significance level <10% via the backward elimination method.
Results
In total, 181 cases of COVID-19 were confirmed, with an attack rate of 4.4%. Of those cases, 12.7% progressed to severe disease, and 8.3% died. In the cohort isolation area on the 8th floor, where 79.0% of the confirmed cases occurred, the adjusted odds ratio was 6.55 (95% CI, 2.99–14.33) and 2.19 (95% CI, 1.24–3.88) for caregivers and the unvaccinated group, respectively. VE analysis revealed that 85.8% of the cases that progressed to severe disease and 78.6% of the deaths could be prevented by administering a second vaccine.
Conclusion
Caregiver training for infection prevention and control is necessary to reduce infection risk. Vaccination is an important intervention to reduce the risk of progression to severe disease and death.

Effectiveness of the COVID-19 vaccine in the Honam region of the Republic of Korea: In-Sook Shin, Yong-Pyo Lee, Seung-Hoon Lee, Jae-Young Lee, Jong-Ha Park, Yoon-Seok Chung; Osong Public Health Res Perspect. 2023;14(3):197-206. Published online June 8, 2023; DOI: https://doi.org/10.24171/j.phrp.2022.0308

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Graphical Abstract Abstract PDF: Objectives
In 2021, the effectiveness of the COVID-19 vaccine was analyzed among people living in the Honam region (Gwangju, Jeollanam-do, Jeollabuk-do, and Jeju) of the Republic of Korea. And we investigated changes in the dominant virus strain.
Methods
This study used the data provided by the Korean Ministry of the Interior and Safety for individuals ≥12 years old in the Honam region, and the Integrated Disease and Health Management System of the Korea Centers for Disease Control and Prevention for COVID-19-vaccinated individuals as of December 31, 2021. Statistical analyzes were performed using IBM SPSS ver. 23.0. The occurrence of confirmed cases by vaccination status, the relative risk, and vaccine effectiveness by vaccine type were calculated.
Results
In 2021, the COVID-19 vaccination rate in Honam was 88.6%. The overall vaccine effectiveness (after 2 and 3 doses) was 98.7% (p<0.001). and the breakthrough infection rate was 0.16%. From week 21 to week 27 of 2021 (June 27 to July 3), the genome sequencing results were mostly alpha variants. The Delta variant emerged as the dominant variant after 27 weeks and the Omicron variant was found at 50 weeks (December 5–11).
Conclusion
Vaccine effectiveness changed with the outbreak of new variants of the virus as well as over time as antibody levels decreased. that the prevention effectiveness of vaccination in Honam was >98%, and the effect among persons who received 2 doses was >90% regardless of the vaccine type. Although vaccine effectiveness decreased because of reduced antibody levels over time (as observed in breakthrough infections), receiving a booster dose restored the neutralizing antibody levels.

mRNA vaccine effectiveness against SARS-CoV-2 B.1.617.2 (Delta) and B.1.1.529 (Omicron) variant transmission from home care cases to household contacts in South Korea: Hanul Park, Young Joon Park, Sang Eun Lee, Min Jei Lee, Hyungtae Ahn; Osong Public Health Res Perspect. 2022;13(6):435-442. Published online November 28, 2022; DOI: https://doi.org/10.24171/j.phrp.2022.0243

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Graphical Abstract Abstract PDF

Objectives
Household contacts of confirmed cases of coronavirus disease 2019 (COVID-19) areexposed to a high risk of viral transmission, and secondary incidence is an important indicatorof community transmission. This study analyzed the secondary attack rate and mRNA vaccineeffectiveness against transmission (VET) for index cases (patients treated at home) confirmedto be infected with the Delta and Omicron variants.Methods: The subjects of the study were 4,450 index cases and 10,382 household contacts.Logistic regression analysis was performed to compare the secondary attack rate byvaccination status, and adjusted relative risk and 95% confidence intervals were identified.Results: The secondary attack rate of the Delta variant was 27.3%, while the secondary attackrate of the Omicron variant was 29.8%. For the Delta variant, groups with less than 90 daysand more than 90 days after 2 doses of mRNA vaccination both showed a VET of 37%. For theOmicron variant, a 64% VET was found among those with less than 90 days after 2 doses ofmRNA vaccination.Conclusion: This study provides useful data on the secondary attack rate and VET of mRNAvaccines for household contacts of COVID-19 cases in South Korea.

Citations

Citations to this article as recorded by

Household secondary attack rates and risk factors during periods of SARS-CoV-2 Delta and Omicron variant predominance in the Republic of Korea
Jin Lee, Mijeong Ko, Seontae Kim, Dosang Lim, Gemma Park, Sang-Eun Lee
Osong Public Health and Research Perspectives.2023; 14(4): 263. CrossRef

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