Estimated SARS-CoV-2 Seroprevalence in Children and Adolescents in Mississippi, May Through September 2020

Case-based tracking of COVID-19 in children and adolescents may underestimate infection, and compared with adults there is little pediatric SARS-CoV-2 seroprevalence data. To assess evidence of previous SARS-CoV-2 infections among children and adolescents in Mississippi, serologic testing for antibodies to SARS-CoV-2 was conducted on a convenience sample of residual serum specimens collected for routine laboratory testing by an academic medical center laboratory during May 17 through September 19, 2020. Seroprevalence by calendar month was standardized to the state population by race/ethnicity; cumulative numbers of infections were estimated by extrapolating seroprevalence to all those aged <18 years in Mississippi. Serum specimens from 1,603 individuals were tested; 175 (10.9%) were positive for SARS-CoV-2 antibodies. Among 1,579 (98.5%) individuals for whom race/ethnicity was known, the number testing positive was 16 (23.2%) of 69 Hispanic individuals, 117 (13.0%) of 901 non-Hispanic Black individuals and 30 (5.3%) of 565 non-Hispanic White individuals. Population-weighted seroprevalence estimates among those aged <18 years increased from 2.6% in May to 16.9% in September 2020. Cumulative numbers of infections extrapolated from seroprevalence data, however, were estimated at 117,805 (95% confidence interval [CI] = 68,771-168,708), suggesting that cases in children and adolescents are much higher than what was reported to the Mississippi State Department of Health (9,044 cases during this period). Further data to appreciate the burden of pediatric disease to inform public health policy is urgently needed.