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Sojin Choi 3 Articles
Viral shedding patterns of symptomatic SARS-CoV-2 infections by periods of variant predominance and vaccination status in Gyeonggi Province, Korea
Gawon Choi, Ah-Young Lim, Sojin Choi, Kunhee Park, Soon Young Lee, Jong-Hun Kim
Epidemiol Health. 2023;45:e2023008.   Published online December 21, 2022
DOI: https://doi.org/10.4178/epih.e2023008
  • 2,642 View
  • 122 Download
  • 1 Web of Science
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
OBJECTIVES
We compared the viral cycle threshold (Ct) values of infected patients to better understand viral kinetics by vaccination status during different periods of variant predominance in Gyeonggi Province, Korea.
METHODS
We obtained case-specific data from the coronavirus disease 2019 (COVID-19) surveillance system, Gyeonggi in-depth epidemiological report system, and Health Insurance Review & Assessment Service from January 2020 to January 2022. We defined periods of variant predominance and explored Ct values by analyzing viral sequencing test results. Using a generalized additive model, we performed a nonlinear regression analysis to determine viral kinetics over time.
RESULTS
Cases in the Delta variant’s period of predominance had higher viral shedding patterns than cases in other periods. The temporal change of viral shedding did not vary by vaccination status in the Omicron-predominant period, but viral shedding decreased in patients who had completed their third vaccination in the Delta-predominant period. During the Delta-predominant and Omicron-predominant periods, the time from symptom onset to peak viral shedding based on the E gene was approximately 2.4 days (95% confidence interval [CI], 2.2 to 2.5) and 2.1 days (95% CI, 2.0 to 2.1), respectively.
CONCLUSIONS
In one-time tests conducted to diagnose COVID-19 in a large population, although no adjustment for individual characteristics was conducted, it was confirmed that viral shedding differed by the predominant strain and vaccination history. These results show the value of utilizing hundreds of thousands of test data produced at COVID-19 screening test centers.
Summary
Korean summary
코로나19 선별진료소에서는 확진 검사를 위해 수십만 건에서 수백만 건까지의 일회성 검사를 시행해왔다. 검사를 받은 개인의 특성과 관련된 데이터 제한으로 인해 분석 시 이를 보정할 수는 없지만, 대규모 인구집단에서 얻어진 검사 결과는 SARS-CoV-2 배출 특성을 평가하는 데 활용될 수 있다. 이번 연구에서는 바이러스 변이의 종류와 백신 접종 이력에 따라 증상 발생 후 시간 경과에 따라 바이러스 배출량이 달라지는 것을 확인하였다. 이러한 대규모 선별 검사자료는 향후에도 유용하게 활용 가능하다.
Key Message
The screening center for COVID-19 has conducted hundreds of thousands to millions of one-time confirmation tests for diagnosis. Although individual characteristics cannot be adjusted for due to data limitations, the test results from a large population can still be utilized to evaluate SARS-CoV-2 shedding. We confirmed that viral shedding varied over time after symptom onset, depending on the type of virus variant and vaccination history.
Direct indicators of social distancing effectiveness in COVID-19 outbreak stages: a correlational analysis of case contacts and population mobility in Korea
Sojin Choi, Chanhee Kim, Kun-Hee Park, Jong-Hun Kim
Epidemiol Health. 2023;45:e2023065.   Published online July 10, 2023
DOI: https://doi.org/10.4178/epih.e2023065
  • 1,157 View
  • 97 Download
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
OBJECTIVES
The effectiveness of social distancing during the coronavirus disease 2019 (COVID-19) pandemic has been evaluated using the magnitude of changes in population mobility. This study aimed to investigate a direct indicator—namely, the number of close contacts per patient with confirmed COVID-19.
METHODS
From week 7, 2020 to week 43, 2021, population movement changes were calculated from the data of two Korean telecommunication companies and Google in accordance with social distancing stringency levels. Data on confirmed cases and their close contacts among residents of Gyeonggi Province, Korea were combined at each stage. Pearson correlation analysis was conducted to compare the movement data with the change in the number of contacts for each confirmed case calculated by stratification according to age group. The reference value of the population movement data was set using the value before mid-February 2020, considering each data’s characteristics.
RESULTS
In the age group of 18 or younger, the number of close contacts per confirmed case decreased or increased when the stringency level was strengthened or relaxed, respectively. In adults, the correlation was relatively low, with no correlation between the change in the number of close contacts per confirmed case and the change in population movement after the commencement of vaccination for adults.
CONCLUSIONS
The effectiveness of governmental social distancing policies against COVID-19 can be evaluated using the number of close contacts per confirmed case as a direct indicator, especially for each age group. Such an analysis can facilitate policy changes for specific groups.
Summary
Korean summary
1. 사회적 거리두기의 효과를 간접적인 자료인 이동통신사와 구글데이터를 이용하여 인구 이동성 변화의 크기를 평가하였고, 직접적인 자료인 역학조사서의 확진자 1인당 밀접 접촉자 수를 산출하여 비교 평가하였다. 2. 18세 이하 연령대는 사회적 거리두기의 강화 또는 완화 단계에 따라 확진자 1인당 밀접 접촉자 수가 민감하게 변동되었으나, 성인의 경우에는 덜 민감하게 변동되었다. 3. 역학조사서에 기반하여 시계열 자료로 재가공한 확진자 1인당 밀접 접촉자 수는 사회적 거리두기 정책의 효과를 평가하는 직접적인 평가 지표로 사용될 수 있기에 충분히 검토되어야 한다.
Key Message
1. The study assessed social distancing's effectiveness by analyzing population mobility changes through mobile operator and Google data. And it was also compared with the number of close contacts per confirmed COVID-19 case based on the epidemiological survey report. 2. Younger age groups were more influenced by the social distancing policy in close contacts per confirmed COVID-19 case than adults. 3. The study suggests using close contacts per confirmed COVID-19 case from the epidemiological survey report as a direct measure of social distancing policy effectiveness.
COVID-19 outbreak in a military unit in Korea
Chanhee Kim, Young-Man Kim, Namwoo Heo, Eunjung Park, Sojin Choi, Sehyuk Jang, Nayoung Kim, Donghyok Kwon, Young-Joon Park, Byeongseop Choi, Beomman Ha, Kyounghwa Jung, Changbo Park, Sejin Park, Heeyoung Lee
Epidemiol Health. 2021;43:e2021065.   Published online September 8, 2021
DOI: https://doi.org/10.4178/epih.e2021065
  • 9,103 View
  • 202 Download
  • 3 Web of Science
  • 2 Crossref
AbstractAbstract AbstractSummary PDF
Abstract
OBJECTIVES
This study presents the response of a military unit to an outbreak of coronavirus disease 2019 (COVID-19) in Gyeonggi Province. As soon as 2 soldiers were identified as index cases, the infectious disease investigators of the Gyeonggi Provincial Government, Korea Disease Control and Prevention Agency, and the Armed Forces Epidemiologic Investigation Center discussed the investigation and response plan for an imminent massive outbreak.
METHODS
The joint immediate response team (IRT) conducted interviews with confirmed COVID-19 patients, reviewed their medical records, performed contact tracing using global positioning system data, and undertook a field investigation. For risk assessment, the joint IRT visited all 8 sites of the military units and the army chaplain’s church to evaluate the transmission risk at each site. The evaluation items included the size of the site, the use of air conditioning, whether windows were opened, and whether masks were worn. Pooled testing was used for the low-risk population to quickly detect the spread of COVID-19 in the military base.
RESULTS
One day before the symptom onset of the index case, the lecturer and >50% of the attendees were infected with COVID-19 while attending a lecture that lasted 2 hours and 30 minutes. Attendees were not wearing masks and were in a poorly ventilated room.
CONCLUSIONS
Since COVID-19 can be spread before symptom onset, contact tracing must be performed to investigate potential exposures prior to symptom onset and to manage any exposed persons.
Summary
Korean summary
본 연구는 경기도 군부대에서 발생한 코로나19 대응 경험을 공유하는 국내 최초의 연구 결과이다. 본 연구를 통해 정리된 역학조사 과정은 군부대, 기숙사, 교정시설 등 집단 시설의 방역 대책 수립에 도움이 될 것으로 기대한다. 또한, 이번 사례는 집단 감염 발생 시 여러 유관 기관의 협조 체계가 신속한 대응과 추가 전파 예방에 중요하다는 점을 시사한다.
Key Message
This study is the first research in South Korea to share the experience of responding to COVID-19 at the military unit in Gyeonggi-do. The epidemiological investigation process organized through this study is expected to help establish response measures for group facilities such as military units, dormitories, and correctional facilities. In addition, this case suggests that the cooperative system of various related organizations in the event of a mass infection is important for rapid response and prevention of further transmission.

Citations

Citations to this article as recorded by  
  • Trends in Confirmed COVID-19 Cases in the Korean Military Before and After the Emergence of the Omicron Variant
    Dong Hoon Shin, Haebong Jang, Sangho Lee, Byung Seop Choi, Donghoon Kim, Hong Sang Oh
    Journal of Korean Medical Science.2022;[Epub]     CrossRef
  • Characteristics of COVID-19 outbreaks and risk factors for transmission at an army training center in South Korea from June to August 2021
    U Jin Cho, Seongjin Wang, Seonju Yi, Yeon Hwa Choi, Eun-Young Kim, Jin A Kim, Sanghwan Bae, Jungyeon Yu, Jangkyu Choi, Young-Joon Park
    Osong Public Health and Research Perspectives.2022; 13(4): 263.     CrossRef

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