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Volume 26, Number 12—December 2020

Interpreting Transmissibility of COVID-19 in Children

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To the Editor: We read with great interest the article by Park et al. (1) on contact tracing of 5,706 patients with coronavirus disease (COVID-19) during the early phase of the pandemic in South Korea. In the study, the overall detection rate of COVID-19 among household contacts was 11.8%; the highest detection rate (18.6%) was in household contacts of those 10–19 years of age and the lowest detection rate (5.3%) in household contacts of those 0–9 years of age. The media have reported the research as evidence that transmissibility in adolescents and adults is similar (2). Such an interpretation may influence decision-making on the reopening of schools.

Although this study nicely demonstrated the effectiveness of contact tracing strategy during a period of school closure, understanding transmissibility and the implications for the reopening of schools requires reinterpretation of the data. As of April 29, 2020, a total of 37.8% of the 10–19 age group were 19 years of age (223/590) and, therefore, were not school children (3). A recently published study in South Korea (4) reported 107 primary source children (aged 0–18) had 248 household contacts and only 1 became infected, giving a secondary attack rate of 0.5%. Data from source and contact tracing in the Netherlands (5) also confirmed low transmissibility in children <18 years of age (0/43, 0%) compared with persons >18 years (55/566, 8.3%).

Accumulating data, including this study, suggest low transmissibility in infected children <10 years of age. However, transmissibility in the adolescent age group is unclear at this time. The 10–19 years age group includes diverse students who have completely different contact patterns from elementary school through college; thus, transmission dynamics of COVID-19 may be different. Further detailed studies on understanding transmissibility of the virus by each school level can provide helpful insights for safe reopening of schools.

Dr. Cho is a clinical associate professor at Department of Pediatrics, Chungnam National University Hospital. Her primary research focuses on pediatric infectious diseases.


Eun Young Cho, Eun Hwa ChoiComments to Author , and Jong-Hyun KimComments to Author 
Author affiliations: Chungnam National University Hospital, Daejeon, South Korea (E.Y. Cho); Seoul National University College of Medicine, Seoul (E.H. Choi); College of Medicine, The Catholic University of Korea, Seoul (J-H. Kim)



  1. Park  YJ, Choe  YJ, Park  O, Park  SY, Kim  YM, Kim  J, et al.; COVID-19 National Emergency Response Center, Epidemiology and Case Management Team. Contact tracing during coronavirus disease outbreak, South Korea, 2020. Emerg Infect Dis. 2020;26:166670. DOIPubMedGoogle Scholar
  2. Mandavilli  A. Older children spread the coronavirus just as much as adults, large study finds. The New York Times. 2020 Jul 18 [cited 2020 Aug 13].
  3. Korea Centers for Disease Control and Prevention. Updates on COVID-19 in Republic of Korea, 29 April 2020 [cited 2020 Nov 13].
  4. Kim  J, Choe  YJ, Lee  J, Park  YJ, Park  O, Han  MS, et al. Role of children in household transmission of COVID-19. Arch Dis Child. 2020 Aug 7 [Epub ahead of print].
  5. National Institute for Public Health and the Environment. Children and COVID-19. 2020 Jul 20 [cited 2020 Aug 13].


Cite This Article

DOI: 10.3201/eid2612.203452

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Table of Contents – Volume 26, Number 12—December 2020

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Please use the form below to submit correspondence to the authors or contact them at the following address:

Jong-Hyun Kim, Department of Pediatrics, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, 93 Jungbu-daero, Paldal-gu, Suwon 16247, South Korea

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Page created: October 05, 2020
Page updated: November 19, 2020
Page reviewed: November 19, 2020
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