Natural course of acute COVID-19 among healthy children in a tertiary hospital

Background: Previous studies have reported the clinical and epidemiological characteristics of children with coronavirus disease 2019 (COVID-19) in a cross-sectional fashion; however, the natural course of each symptom based on a daily basis during the acute phase has not yet been clarified. This retrospective study aimed to describe the natural course of COVID-19 in children according to dominant variants.Methods: We conducted our study on symptomatic children with COVID-19 who were hospitalized at the National Center for Child Health and Development, in Japan. We excluded patients who were observed for less than 9 days and those with underlying disease, COVID-19 vaccination, coinfection, complications, or therapeutic intervention. We collected the data on each participant's age at admission, sex, medical history, observation period, hospitalization period, SARS-CoV-2 test results, and 10 daily symptoms in the first 9 days from the illness onset.Results: Eventually, 115 children were included in this study. The prevalence of fever during the omicron era declined more rapidly over time than that during the pre-omicron era. The prevalence of cough and rhinorrhea did not decline during the observation period, and these clinical manifestations were more common during the pre-omicron era at any point. The prevalence of dysgeusia and/or dysosmia steadily increased over time in the pre-omicron era. This study demonstrated that the prevalence of some symptoms differed not only at the onset but also over time during the acute phase.Conclusion: Details of the natural clinical course of children with COVID-19 help primary care physicians to manage these patients.