Predictors of Severe Acute Respiratory Syndrome Coronavirus 2 Seropositivity Before Coronavirus Disease 2019 Vaccination Among Children 0–4 Years and Their Household Members in the SEARCh Study

Abstract

Background Estimates of SARS-CoV-2 seroprevalence in young children and risk factors for seropositivity are scarce. Using data from a prospective cohort study of households during the pre-COVID-19 vaccine period, we estimated SARS-CoV-2 seroprevalence by age and evaluated risk factors for SARS-CoV-2 seropositivity. Methods The SARS-CoV-2 Epidemiology and Response in Children (SEARCh) study enrolled 175 Maryland households (690 participants) with ≥1 child aged 0-4 years during November 2020―March 2021; individuals vaccinated against COVID-19 were ineligible. At enrollment, participants completed questionnaires about sociodemographic and health status, and work, school, and daycare attendance. Participants were tested for SARS-CoV-2 antibodies in sera. Logistic regression models with generalized estimating equations (GEE) to account for correlation within households assessed predictors of individual- and household-level SARS-CoV-2 seropositivity. Results Of 681 (98.7%) participants with enrollment serology results, 55 (8.1%, 95% CI: 6.3-10.4%) from 21 (12.0%) households were seropositive for SARS-CoV-2. Among seropositive participants, fewer children than adults reported being tested for SARS-CoV-2 infection before enrollment (odds ratio [OR] = 0.23, 95%CI: 0.06-0.73). Seropositivity was similar by age (GEE OR vs 0-4y: 1.19 for 5-17y, 1.36 for adults; p = 0.16) and was significantly higher among adults working outside the home (GEE aOR = 2.2, 95%CI: 1.1-4.4) but not among children attending daycare or school. Conclusions Prior to study enrollment, children and adults in this cohort had similar rates of SARS-CoV-2 infection as measured by serology. An adult household member working outside the home increased a household’s odds of SARS-CoV-2 infection, whereas a child attending daycare or school in person did not.