Radtke T, Ulyte A, Puhan MA, et al. - Symptoms compatible with long COVID were less prevalent in a randomly selected cohort of children assessed 6 months after serologic testing.

• From randomly selected schools from the 12 cantonal districts, children of randomly selected classes were invited to participate and participants underwent 3 testing phases including collection of venous blood for serologic analysis and online questionnaires for symptoms.

• Children who tested positive for SARS-CoV-2 antibodies in October or November 2020 were compared with those who tested negative.

• Of 2,503 children (54%) with a serology result in October or November 2020, 1,355 were eligible for Inclusion (median age, 11 years; interquartile range, 9-13 years; 54% girls).

• Findings suggest the existence of long COVID in children; at least 1 symptom lasting beyond 12 weeks was reported in 4 of 109 seropositive children (4%) vs 28 of 1,246 seronegative ones (2%).

• Among seropositive children, tiredness (3/109 [3%]), difficulty concentrating (2/109 [2%]), and increased need for sleep (2/109 [2%]) were the most frequently documented symptoms lasting more than 12 weeks. .

• Evidence suggest that estimates of the prevalence of persisting symptoms range from 0% to 27%.

• The variability in prevalence estimates is likely due to initial SARS-CoV-2 infection severity, different methodological approaches (clinical assessment vs self-report), definition of cases (diagnosed vs suspected), variable follow-up times, and prevalence of preexisting clinical conditions.