Geospatial Analysis of Age-specific SARS-CoV-2 Transmission Patterns in Households, Korea

Seonju Yi,Young-Man Kim,최영준,Seonhee Ahn,Sohee Han,Young-Joon Park 대한의학회 2021 Journal of Korean medical science Vol.36 No.8

We constructed an age-to-age infection matrix to characterize the household transmission pattern of coronavirus disease 2019 (COVID-19) in Korea. Among 4,048 household clusters, within-age group infection dominated the overall household transmissions. Transmission of severe acute respiratory syndrome coronavirus 2 was more common from adults to children than from children to adults.

SARS-CoV-2 Delta Variant Breakthrough Infection and Onward Secondary Transmission in Household

Yi Seonju,Kim Jong Mu,최영준,Hong Sujin,Choi Siwon,Ahn Seong Bae,Kim Miya,Park Young-Joon 대한의학회 2022 Journal of Korean medical science Vol.37 No.1

Background: Despite the extraordinary speed of mass vaccination efforts, an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant in a vaccinee with coronavirus disease 2019 (COVID-19) mRNA vaccine was identified in an adult day service center (ADSC) of Jeju, South Korea. The primary objective of this study was to investigate the epidemiologic features in infection-vulnerable facilities with a high vaccination rate of BNT162b2 mRNA COVID-19 vaccine. The second was to estimate the secondary transmission prevention effect of the vaccine in the household members by vaccination status. Methods: We included all ADSC participants, staff and their household members. All COVID-19 infected cases were confirmed by reverse transcriptase polymerase chain reaction. We calculated attack rate in ADSC and the secondary attack rate (SAR) in household members by vaccination status. Results: Among a total of 42 participants and 16 staff, of which 96.6% were fully vaccinated with BNT162b2 mRNA COVID-19 vaccine, 12 symptomatic cases and 13 asymptomatic confirmed cases of COVID-19 were found. The attack rate was 43.1%, with 13 isolates identified as SARS-CoV-2 virus, delta variant. The SAR in unvaccinated and partially vaccinated household members were 27.8% (5/18) and 25.0% (5/20), respectively, while the SAR in fully vaccinated household members was 12.5% (1/8). Conclusion: We describe a SARS-CoV-2 delta variant outbreak in ADSC with high vaccine coverage rate, characterized by high infection rate, high transmissibility, and low clinical severity. The outbreak proceeded to unvaccinated or partially vaccinated household members, emphasizing the need for immunizing close contacts of high-risk groups.

Unequal Geographic Distribution of Life Expectancy in Seoul

Kim, Sangmi,Yi, Seonju,Kim, Meekyung,Kim, Bokyung,Lee, Hwayoung,Jeon, Taekryeon,Cho, Youngtae SAGE Publications 2015 Asia-Pacific journal of public health Vol.27 No.2

<P>This study examined life expectancies in 25 <I>gu</I>s, administrative districts of Seoul, the capital of Korea, by gender in 1995, 2002, and 2008 to explore trends in mortality inequality among areas. The authors constructed single-decrement life tables and employed between-group variance, the Theil index, and mean log deviation to measure absolute and relative disparities in life expectancy among areas during the periods 1995-2002 and 2002-2008. It was found that life expectancy gaps between <I>gu</I>s have widened in absolute and relative terms in both genders over the decade, and that this pattern was particularly dramatic in females after 2002. This increasing gap could be attributable to the more negative health impact on females since the late 1990s stemming from the economic crisis, eventually reflected in their places of residence. Thus, a social buffer system to narrow the health gap between geographic areas and social classes must be established.</P>

Recent increase in pertussis incidence in South Korea: An age-period-cohort analysis

Kim Chanhee,Yi Seonju,Cho Sung-il 한국역학회 2021 Epidemiology and Health Vol.43 No.-

OBJECTIVES: Pertussis or whooping cough—one of the most contagious diseases—is caused by the Gram-negative bacterium Bordetella pertussis. Despite a high vaccination rate, Korea recently experienced a resurgence of pertussis. This study explores patterns and possible explanations for this resurgence through an age-period-cohort analysis. METHODS: Using secondary data from the infectious disease portal of the Korea Disease Control and Prevention Agency and the Korea Statistical Information Service of Statistics Korea, this study analyzed the incidence of pertussis in Korea to determine which factors contributed to the recent increase using an age-period-cohort model. RESULTS: Analysis of the age effect indicated that the age group most vulnerable to pertussis was 0-year to 2-year-olds. Analysis of the period effect showed a sharp increase in the incidence rate after 2016. Analysis of the cohort effect showed a significant decrease in incidence beginning with the 1955 birth cohort, with the risk increasing again with the 2000s birth cohort. CONCLUSIONS: Previous studies have suggested 3 main possible explanations for our results. First, the increased incidence rate can be attributed to contact rates. Second, the rate of immunity through natural exposure has decreased due to the low number of circulating pathogens, in turn affecting the trend of infection. Lastly, variations in pathogens may have also contributed to the increase in incidence. Given that the most significant increase in incidence was observed among infants younger than 1 year old, sufficient maternal immunity must be prioritized to provide passive immunity to newborns via the placenta.

Characteristics of COVID-19 outbreaks and risk factors for transmission at an army training center in South Korea from June to August 2021

조유진,왕성진,Yi Seonju,Yeon Hwa Choi,김은영,김진아,배상환,유정연,최장규,박영준 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.4

Objectives: It is crucial to establish the characteristics of coronavirus disease 2019 (COVID-19) outbreaks at army training centers to develop preventive measures. Therefore, this study aimed to determine the COVID-19 transmission patterns and risk factors in a sequence of outbreaks at an army training center from June to August 2021.Methods: This study included 1,324 trainees at an army training center where outbreaks occurred from June to August 2021. The outbreak was qualitatively analyzed according to the period, attack rate, demographic characteristics, vaccination history, and living areas. An aerodynamic experiment was performed to evaluate aerosol transmission in living areas.Results: Three outbreaks occurred at the army training center from June to August 2021. The first, second, and third outbreaks lasted for 32, 17, and 24 days, and the attack rates were 12.8%, 18.1%, and 8.9%, respectively. Confirmed cases were distributed in all age groups. Recruits and the unvaccinated were at higher risk for COVID-19. The aerodynamic experiment verified the possibility of aerosol transmission within the same living area.Conclusion: COVID-19 transmission at army training centers should be minimized through quarantine and post-admission testing during the latency period as part of integrated measures that include facility ventilation, vaccination, indoor mask-wearing, and social distancing.

Vaccine Effectiveness Against Severe Disease and Death for Patients With COVID-19 During the Delta-Dominant and Omicron-Emerging Periods: A K-COVE Study

Kim Yoo-Yeon,최영준,Kim Jia,Kim Ryu Kyung,Jang Eun Jung,Lee Hyeryeon,Yi Seonju,Lee Sangwon,Park Young-Joon 대한의학회 2023 Journal of Korean medical science Vol.38 No.11

National cohort data collected during the coronavirus disease 2019 (COVID-19) delta and omicron periods in Korea revealed a lower risk of severe infection in recipients of three doses of the COVID-19 vaccine (adjusted odds ratio [aOR], 0.05–0.08). The risk of death was reduced during the omicron period compared to the delta period (aOR, 0.75; 95% confidence interval, 0.67–0.84).

Presumed population immunity to SARS-CoV-2 in South Korea, April 2022

Eun Jung Jang,Choe Young June,Choe Seung-Ah,Yoo-Yeon Kim,Ryu Kyung Kim,Jia Kim,Lim Dosang,Ju Hee Lee,Yi Seonju,Sangwon Lee,Young-Joon Park 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.5

Objectives: We estimated the overall and age-specific percentages of the Korean population with presumed immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as of April 2022 using the national registry. Methods: We used the national coronavirus disease 2019 (COVID-19) infection and vaccination registry from South Korea, as described to define individuals with a previous history of COVID-19 infection, vaccination, or both, as persons with presumed immunity.Results: Of a total of 53,304,627 observed persons, 24.4% had vaccination and infection, 58.1% had vaccination and no infection, 7.6% had infection and vaccination, and 9.9% had no immunity,. The SARS-CoV-2 Omicron variant emerged at a time when the presumed population immunity ranged from 80% to 85%; however, nearly half of the children were presumed to have no immunity.Conclusion: We report a gap in population immunity, with lower presumed protection in children than in adults. The approach presented in this work can provide valuable informed tools to assist vaccine policy-making at a national level.

Early Intervention Reduces the Spread of COVID-19 in Long-Term Care Facilities in the Republic of Korea

Park Shin Young,Choi Gawon,Lee Hyeyoung,Kim Na-young,Lee Seon-young,Kim Kyungnam,Shin Soyoung,Jang Eunsu,Moon YoungSin,Oh KwangHwan,Choi JaeRin,Lee Sang-Eun,Kim Young-Man,Kim Jieun,Yi Seonju,Gwack Jin 질병관리본부 2020 Osong Public Health and Research Persptectives Vol.11 No.4

This study describes the epidemiological characteristics of coronavirus disease 2019 (COVID-19) based on reported cases from long-term care facilities. As of April 20th, 2020, 3 long-term care facilities in a metropolitan area of South Korea had reported cases of COVID-19. These facilities’ employees were presumed to be the sources of infection. There were 2 nursing hospitals that did not report any additional cases. One nursing home had a total of 25 cases, with an attack rate of 51.4% (95% CI 35.6–67.0), and a fatality rate of 38.9% (95% CI 20.3–61.4) among residents. The results from this study suggest that early detection and maintenance of infection control minimizes the risk of rapid transmission.