Cohort profile: the SEROCoV-KIDS population-based cohort study and biobank on the impact of the COVID-19 pandemic in children and adolescents in Geneva, Switzerland.

purposeThe COVID-19 pandemic raised major concerns about its potential effects on children and adolescents, particularly through disruptions to their health, social and educational environments and the exacerbation of existing inequalities. In response to the limited evidence-based knowledge available at the time, the SEROCoV-KIDS study was launched in 2021 as a prospective cohort and biobank to assess the pandemic's effects on youth health and well-being. It focuses on the general population of Geneva, Switzerland, as well as subgroups with vulnerabilities, including prior SARS-CoV-2 infection, chronic health conditions and socioeconomic disadvantage.

participantsA total of 2199 children and adolescents, aged 6 months to 17 years, from 1340 households were enrolled in the SEROCoV-KIDS cohort, 2048 from the general population and 151 from clinics (ie, children with chronic health conditions). At baseline, between December 2021 and June 2022, participants provided blood samples for serological testing and for long-term storage in the biobank, while comprehensive questionnaires were completed by a referent adult and adolescents aged 14 and older. Five follow-up online assessments were conducted until October 2026, addressing physical and mental health, development, quality of life, health behaviours, family dynamics and education-related topics. The quantitative findings of the cohort study were enriched by a cross-sectional qualitative study conducted between October 2023 and March 2024, focusing specifically on socioeconomically disadvantaged populations. FINDINGS TO DATE: In the population-based sample, 66.3% of participants tested seropositive for anti-SARS-CoV-2 nucleocapsid antibodies at baseline, and 4.1% reported symptoms consistent with post-COVID-19 condition. Most children were minimally or not at all affected by the pandemic, showing good mental health over time. However, 8% of participants reported a positive pandemic impact, whereas 8%-13% experienced negative impacts, mainly due to disrupted routines and reduced social support. Health behaviours like physical activity and sleep remained largely stable over the study period. Higher screen time at baseline was associated with poorer well-being. Children with chronic health conditions or experiencing socioeconomic and family disadvantage were disproportionately affected in terms of the health and psychosocial consequences of the pandemic. FUTURE PLANS: SEROCoV-KIDS demonstrates the value of child-focused cohorts for understanding the consequences of major societal events and for guiding evidence-based policy. Our next priority is to secure funding to prolong follow-up of this cohort and to maintain systematic surveillance of children and adolescents, so that emerging findings can directly inform public health and education policy over the coming years.