Susceptibility to Sars-COV-2 Infection Among Children And Adults: A Seroprevalence Study of Family Households in the Barcelona Metropolitan Region, Spain

Clin Infect Dis. 2020 Nov 12;ciaa1721. doi: 10.1093/cid/ciaa1721. Online ahead of print.


Background: Susceptibility of children and adults to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and persistence of antibody response to the virus after infection resolution remain poorly understood, despite their significant public health implications.

Methods: A cross-sectional seroprevalence study with prospective recruitment of volunteer families that included at least one first-reported adult case positive by SARS-CoV-2 PCR and at least one child aged less than 15 years living in the same household under strict home confinement was conducted in the Health Region of metropolitan Barcelona (Spain) during the pandemic period April 28-June 3, 2020. All household members were tested at home by a rapid SARS-CoV-2 antibody assay in finger-prick obtained capillary blood.

Results: A total of 381 family households including 381 first-reported PCR-positive adult cases and 1,084 contacts (672 children, 412 adults) were enrolled. SARS-CoV-2 infection seroprevalence rates were 17.6% (118/672) in children and 18.7% (77/335) in adult contacts (p=0.64). Among first-reported cases, seropositivity rates varied from 84.0% in adults previously hospitalized and tested within 6 weeks since the first positive PCR result to 31.5% in those not hospitalized and tested after that lag time (p<0.001). Nearly all (99.9%) positive pediatric contacts were asymptomatic or had mild symptoms.

Conclusion: Children appear to have similar probability as adults to become infected by SARS-CoV-2 in quarantined family households but remain largely asymptomatic once infected. Adult antibody protection against SARS-CoV-2 seems to be weak at early convalescence and beyond 6 weeks post-infection confirmation, especially in cases that have experienced mild disease.

Keywords: COVID-19; SARS-CoV-2; antibody; children; household; prevalence.