Pediatric Infection-Induced SARS-CoV-2 Seroprevalence Increases and Seroprevalence by Type of Clinical Care-September 2021 to February 2022

Background Trends in estimates of US pediatric SARS-CoV-2 infection-induced seroprevalence from commercial laboratory specimens may overrepresent children with frequent health care needs. We examined seroprevalence trends and compared seroprevalence estimates by testing type and diagnostic coding. Methods Cross-sectional convenience samples of residual sera September 2021-February 2022 from 52 US jurisdictions were assayed for infection-induced SARS-CoV-2 antibodies; monthly seroprevalence estimates were calculated by age group. Multivariate logistic analyses compared seroprevalence estimates for specimens associated with International Classification of Diseases-Tenth Revision (ICD-10) codes and laboratory orders indicating well-child care with estimates for other pediatric specimens. Results Infection-induced SARS-CoV-2 seroprevalence increased in each age group, from 30% to 68% (1-4 years), 38% to 77% (5-11 years), and 40% to 74% (12-17 years). On multivariate analysis, patients with well-child ICD-10 codes were seropositive more often than other patients aged 1-17 years (adjusted prevalence ratio [aPR] 1.04; 95% confidence interval [CI], 1.02-1.07); children aged 9-11 years receiving standard lipid screening were seropositive more often than those receiving other laboratory tests (aPR, 1.05; 95% CI, 1.02-1.08). Conclusions Infection-induced seroprevalence more than doubled among children younger than 12 years between September 2021 and February 2022, and increased 85% in adolescents. Differences in seroprevalence by care type did not substantially impact US pediatric seroprevalence estimates. Epidemiologically important differences in infection-induced SARS-CoV-2 antibody seroprevalence estimates were not seen between children receiving well-child care and those with acute or chronic conditions, indicating that care type is not an important source of bias for US pediatric seroprevalence estimates.

Automated summary

The seroprevalence of infection-induced SARS-CoV-2 antibodies more than doubled among children younger than 12 years between September 2021 and February 2022, and increased by 85% in adolescents. The differences in seroprevalence estimates by care type did not significantly impact US pediatric seroprevalence estimates.