Prevalence and risk factors of post-coronavirus disease 2019 condition among children and adolescents in Japan: A matched case-control study in the general population

•Post-COVID-19 condition (PCC) was threefold higher in patients than in controls.•Patients with alpha and delta variants had higher PCC than those with omicron.•Among patients with PCC, 11% reported severe impairment >6 months after infection.•Two prior vaccination doses halved PCC risk and could be a promising approach. To examine prevalence and risk factors for post-COVID-19 condition (PCC) in a paediatric population. The study included patients aged 5-17 years with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection between 1 March 2021 and 30 April 2022 and matched non-infected controls from Yao City, Japan. We compared parent-reported symptoms persisting ≥2 months (present at 3 months post-infection for patients) between the groups. COVID-19 vaccination data was obtained from the Vaccination Registry. Among 8167 invited individuals, 3141 (1800 cases, mean age: 10.4 years, 46.1% females; 1341 controls, mean age 10.5 years, 47.1% females) participated. Patients had elapsed average 273 (185-605) days from infection, and 1708 (94.9%) experienced mild acute symptoms. Patients had higher odds of having persistent symptoms than did controls (6.3% vs 2.2%, adjusted odds ratio [aOR]: 3.15, 95% confidence interval: 2.08-4.77), with 53.6% of them reporting current disruption due to the symptoms. Older age, low household income, pre-existing allergy, and autonomic nervous system disease were associated with increased risks of developing PCC; two prior vaccination doses reduced these risks (aOR: 0.53, 0.29-0.96). SARS-CoV-2 infection, including omicron infections heighten persistent symptom risk in the paediatric population, necessitating preventive strategies, notably vaccination.