Study population and setting
This prospective cohort, called Ciao Corona, evaluated the long-term symptoms of COVID-19 in children and adolescents at 55 randomly selected schools in the canton of Zurich, Switzerland. Among participating schools, the students of randomly selected classes were invited to participate. The study included children and adolescents who tested positive for SARS-CoV-2 antibodies based on serologic test in October/November 2020 and had follow-up in March/April 2021 and a comparison group of children who were seronegative in October/November 2020 and March/April 2021. A questionnaire administered to the parents of participating students asked about symptoms experienced by the children since October 2020 that lasted for 1) at least 4 weeks and 2) more than 12 weeks.
Summary of Main Findings
Of 2503 potentially eligible students, only 1355 (54%) were included (median age: 11 years, 54% female). Of these, 109 (8%) were seropositive. Seropositive and seronegative participants experienced similar amounts of symptoms lasting >4 weeks (report of ≥1 symptom: 9% seropositive vs. 10% seronegative), but seropositive participants experienced minimally higher amounts of symptoms lasting >12 weeks (report of ≥1 symptom: 4% vs. 2%). The most common symptoms at 12 weeks were tiredness (seropositive vs. seronegative: 3% vs. 1%), difficulty concentrating (3% vs. 1%), and increased need for sleep (2% vs. 0%), but the rates of these symptoms were low in both groups. Students in both groups had similar reports of excellent or good health (seropositive vs. seronegative: 94% vs. 96%).
This was a prospective study of randomly selected students, who should be relatively representative of all school-aged children and adolescents in Switzerland. The study includes a population-based seronegative control group.
A major limitation of the study is the retrospective reporting of symptoms from the parents of the children included. Recall bias is quite possible, which could lead to over-reporting of symptoms among parents who knew their children had COVID-19 during the study period. Additionally, many students were excluded because they seroconverted during the study period (N=238), were not tested (N=292), or didn’t provide information on symptoms (N=618). Analyses were descriptive and did not account for any pre-existing conditions or pre-illness health. It is also unclear whether additional illness during the study period could have contributed to the observed results.
This study is one of the first to provide population-based estimates of long COVID symptoms in children and adolescents, compared to a well-defined control group.
This review was posted on: 1 September 2021