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Role of children in household transmission of COVID-19

Our take —

Given extensive social distancing measures and rigorous testing and contact tracing, the secondary transmission rate from pediatric COVID-19 cases to secondary cases in the early phase of the South Korean epidemic was low. It is not clear how generalizable these findings are.

Study design

Case Series

Study population and setting

Between January 20 and April 6 2020, all identified pediatric (aged 18 years old or younger) index cases of COVD-19 (n=107) and their household contacts (n=248) in South Korea were identified and reviewed from the National Notifiable Disease Surveillance System. From these data, the secondary attack rate from children to their household contacts was calculated [(secondary case/traced N) x 100%]. Children were confirmed positive through RT-PCR testing, and household contacts were screened through RT-PCR and then placed on a 14-day quarantine regardless of symptoms

Summary of Main Findings

The median age of pediatric index cases was 15 years old (IQR: 10-17). The average number of household contacts per index case was 4.3 (range: 1-67). Of the 41 contacts who were confirmed to have COVID-19, 40 of those had the same exposure as the pediatric index case and were therefore not classified as secondary cases. Only 1 index case-secondary case pair was identified: a 16-year old index case who had returned from the UK to Korea and her 14-year old secondary case sibling, yielding a secondary attack rate of 0.5% (95% CI 0.0% to 2.6%).

Study Strengths

This study represents all identified pediatric index cases of COVID-19 in the early phase of the pandemic and thorough testing and tracing data are available through South Korea’s National Notifiable Disease Surveillance System.

Limitations

These data represent the role of children in household transmission during a period in which schools were closed. These findings should not be extrapolated to settings in which schools have reopened and children have greater mobility and risk of exposure outside the home. No comparison is provided to adults to see how different the results are by age. There is also potential for selection bias in that the cases were only those that were identified and reported. It is also unclear what precautions were being taken within households to prevent transmission.

Value added

This study presents findings on the secondary attack rate from pediatric index cases to household contacts during the early phase of the pandemic within a specific context, that of households in South Korea in the early stages of the epidemic.

This review was posted on: 11 September 2020