During the COVID-19 pandemic, longitudinal serological surveillance was critical to accurately assess the cumulative incidence of COVID-19 and monitor population-level immunity among children. We characterized the epidemiology of COVID-19 among North and South Carolina children using remote electronic symptom surveillance and serial at-home antibody testing in 2–17-year-old children from April to December 2021. We estimated accumulation of infection-induced antibodies, defined as seropositivity before vaccination. Reported novel symptoms were characterized for seropositive and seronegative participants. A total of 1058 children (median age 10 years (IQR 7–13)) participated in symptom surveillance. Estimated cumulative prevalence of infection-induced antibody increased from 0% (0–60%) to 85.7% (31.6–97%), 3.1% (0–9.0%) to 61.7% (46.1–72.7%) and 5.6% (0–15.6%) to 75% (59.9–84.4%), respectively, among those aged 2–4, 5–11 and 12–17 years. Determinants of seropositivity included Black race (OR 2.06 (1.19 to 3.47)) and having >5 household members (OR 3.05 (1.21 to 7.45)). Participants seroconverting reported mostly respiratory or systemic symptoms, but 52% (28/52) were asymptomatic. We demonstrate the role of at-home testing in trending SARS-CoV-2 seroprevalence in a community cohort of children. Such regional serological surveillance complements national data for a more complete assessment of SARS-CoV-2 burden and transmission. Future applications of the remote surveillance platform may be leveraged for characterizing the epidemiology of novel pathogens.
