Prevalence of SARS-CoV-2 Infection in Children and Their Parents in Southwest Germany

Abstract

Background: School and day-care closures were enforced as measures to confine the COVID-19 pandemic based on the assumption that young children may play a key role in SARS-CoV-2 spreading. However, infection prevalence in children under 10 years of age is not very well analysed. Methods: The COVID-19 BaWu study is a large-scale multicentre cross-sectional investigation of children aged 1–10 years and one of their parents, both not diagnosed with COVID-19 before, in southwest Germany. We tested for SARS-CoV-2 RNA from nasopharyngeal swabs by RT-PCR and for SARS-CoV-2 specific IgG antibodies in serum by ELISA and immunofluorescence. Discordant results were clarified by ECLIA, a second ELISA or an in-house Luminex-based assay. We used mixed effects logistic regression to estimate the seroprevalence and to analyse the association between SARS-CoV-2 seropositivity and covariates. Findings: Between April 22nd and May 15th, 2020, we enrolled 4964 subjects, 2482 children and 2482 corresponding parents. 0•04% tested positive for SARS-CoV-2 RNA. The estimated SARS-CoV-2 seroprevalence was low in parents (1•8%; 95% CI, 1•2–2•4%) and 3-fold lower in children (0•6%; 95% CI, 0•3–1•0%). We observed virus-neutralizing activity for 66 of 70 IgG-positive sera (94•3%). Interpretation: The spread of SARS-CoV-2 infection during a period of lock-down in southwest Germany was particularly low in children aged 1–10 years. Accordingly, it is unlikely that children have boosted the pandemic. This largest reported SARS-CoV-2 prevalence study focussing on children is instructive for how ad hoc mass testing provides the basis for rational political decision making in a pandemic setting. Funding: Grant from the Federal State of Baden-Wurttemberg, Germany Declaration of Interests: All authors state no conflict of interest. Ethics Approval Statement: The study protocol was approved by the independent Ethics committees of each centre. The study was conducted according to the Declaration of Helsinki. Written informed consent was obtained from all parents/guardians, with assent from children when appropriate for their age.