Long COVID in children and adolescents: Incidence and clinical characteristics in Buenos Aires, 2021-2023.

Introduction. Long COVID affects approximately 8.5% of the pediatric and adolescent population after SARS-CoV-2 infection, and vaccination could reduce its incidence. Objectives. To determine the incidence of long COVID in children and adolescents aged 5 to 18 years, describe symptoms and duration, analyze differences by age and sex, estimate reinfections and school absenteeism, and evaluate its relationship with vaccination. Population and methods. Prospective cohort study conducted between August 1, 2021, and February 1, 2023. To calculate incidence, patients with COVID-19 treated at a general acute care hospital in the Autonomous City of Buenos Aires were included; for characterization, cases referred from other centers were included as well. Descriptive and comparative analyses were performed, estimating incidence with 95% CI; STATA 14.0 was used (p <0.05). The study was approved by the Ethics Committee. Results. Of 496 patients, 475 were included, and 21 were excluded due to severe comorbidities. The incidence of long COVID was 7.79% (95% CI 5.37-10.21). Those affected had a higher mean age (12.57 vs. 11.20 years; p = 0.02) and a higher incidence in unvaccinated or partially vaccinated individuals (11.48% vs. 5.48%; p = 0.018). The most common symptoms were fatigue, cough, and myalgia. Conclusion. The incidence of long COVID was comparable to that reported in other pediatric series. A lower incidence was observed in children and adolescents with complete vaccination schedules, and fatigue was the most frequent clinical manifestation. These findings reinforce the need to continue generating evidence.