The clinical characteristics of pediatric coronavirus disease 2019 in 2020 in Japan.

BACKGROUND: Coronavirus disease 2019 (COVID-19) pandemic has affected the lives of young and old people. Most reports on pediatric cases suggest that children experience fewer and milder symptoms than adults do. This is the first nationwide study that focused on pediatric cases reported by pediatricians, including those with no or mild symptoms, in Japan. METHODS: We analyzed the epidemiological and clinical characteristics, and transmission patterns of 840 pediatric (<16 years old) COVID-19 cases reported between February and December 2020 in Japan, using a dedicated database that was voluntarily registered by the members of the Japan Pediatric Society. RESULTS: Almost half of patients (47.7%) were asymptomatic, while most of the others presented mild symptoms. At the time of admission or first outpatient clinic visit, 84.0% of the cases were afebrile (<37.5°C). In total, 609 cases (72.5%) were exposed to COVID-19-positive household members. We analyzed the influence of nationwide school closures that were introduced in March 2020 on COVID-19 transmission routes among children in Japan. Transmission within households occurred most frequently, with no significant difference between the periods before and after declaring nationwide school closures (70.9% and 74.5%, respectively). CONCLUSIONS: COVID-19 symptoms in pediatric cases are less severe than those in adult cases. School closure appeared to be limitedly effective, and controlling household transmission from adult family members is the most important measure for COVID-19 prevention among children.