SARS-CoV-2 Infection of Schoolchildren in Austria at the Beginning of the Pandemic

BACKGROUND: Children seem to be less often affected by a SARS-CoV-2 infection, and generally have a less severe clinical course. However, robust data on COVID-19 prevalence and seroprevalence in children is lacking.   METHODS: We conducted a cross-sectional study in May-July 2020 on 2069 urban schoolchildren and adolescents (median age 13 years, IQR 10-15) in Vienna, Austria, to assess current SARS-CoV-2 infection (real-time RT-PCR) and antibody prevalence (immunoassay). School authorities approached parents for voluntary participation stratified for age and socioeconomic status. Consenting families were contacted by the study team. A nasal and oropharyngeal swab, a blood sample, and a questionnaire were employed. Primary endpoint was frequency of SARS-CoV-2 real-time RT-PCR-positive and seropositive children.      FINDINGS: Of 2069 children (52·4% female) 600 were 5-10 years of age (44·7% female), 825 were 11-14 years of age (49·9% female), and 644 were 15-21 years of age (62·7% female). Response rate to study invitation was 72·7%. Two cases tested positive for SARS-CoV-2 RNA (0·1%), and 26 cases tested positive for specific antibodies using multiple immunoassays including a virus neutralization test (1·3%). Antibody test positivity was assigned with mild clinical symptoms in 14 children (53·8%), whereas 12 children (46·2%) had not reported any symptoms in the weeks prior to investigation. Within the seropositive children being tested concomitantly with their siblings (n=13; 7 with 1, 4 with 2 and 2 with 3 siblings), only one sibling pair of siblings was seropositive.  INTERPRETATION: In our study cohort SARS-CoV-2 seroprevalence and infection rate were low and all affected children and adolescents reported mild symptoms or remained asymptomatic. Virus spreading seemed to occur more likely in intergenerational contacts than among siblings in the same household.   FUNDING: Medical Scientific Fund of the Mayor of the City of Vienna (Grant Covid028) (Medizinisch-Wissenschaftlicher Fonds des Burgermeisters der Bundeshauptstadt Wien) DECLARATION OF INTERESTS: The authors declare no competing interests. ETHICS APPROVAL STATEMENT: The study was designed as an academic study and was approved by the Ethics Committees of the Medical University of Vienna (EK1401/2020), the Municipal Hospitals of Vienna (EK20-085-VK) and the Private Sigmund Freud University (EK148/2020). Different forms of informed consent were used for children of ages 5- 7y, 8-14y, and 15-18y, and for parents or legal guardians of participant children and adolescents.