The Seroprevalence of SARS-CoV-2 in Children During Early COVID-19 Pandemic in Korea: A Nationwide, Population-Based Study

BACKGROUND: Coronavirus disease 2019 (COVID-19) is often asymptomatic and associated with mild clinical symptoms in children. Social distancing measures have led to a relatively small number of confirmed COVID-19 cases in Korea than in other countries in the earlier pandemic phase. Previous seroprevalence studies in Korean adults before the introduction of COVID-19 vaccination campaign have shown a low antibody positivity rate. However, data on COVID-19 seroprevalence in Korean children remained scarce. In this study, we assessed the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children in Korea. METHODS: Between December 2020 and March 2021, stratified serum samples were collected from children aged 0–18 years in 17 different regions across the country. The SARS-CoV-2 antibody test was conducted using an electro-chemiluminescence immunoassay (ECLIA) to detect the antibodies against nucleocapsid antigens of SARS-CoV-2. Samples that tested positive using the ECLIA were reflexed to an additional plaque reduction neutralization test (PRNT) for SARS-CoV-2. RESULTS: A total of 1,887 samples were collected. Excluding 21 samples collected from regional medical centers, 1,866 samples were included in the final analysis. Two samples (0.11%) were positive for the antibodies against nucleocapsid antigens of SARS-CoV-2. Both samples were shown to have neutralizing antibodies for SARS-CoV-2 via PRNT. CONCLUSION: After 1 year since the start of COVID-19 pandemic, the seroprevalence of SARS-CoV-2 among Korean children was 0.11%, which was lower than the adults (0.52%) in another study conducted during a similar period. In the early stages of the COVID-19 pandemic, the seroprevalence of SARS-CoV-2 in Korea was lower than those of other countries, which was presumed to be the consequence of a very strong social distancing measures.