Incidence rates and symptomatology of community infections with SARS-CoV-2 in children and parents: The CoKids longitudinal household study

AIMThe CoKids study aimed to estimate the community incidence of symptomatic and asymptomatic SARS-CoV-2 in children and parents and to assess the symptomatology of SARS-COV-2 infections relative to SARS-CoV-2 negative respiratory episodes. METHODSIn this prospective study, households with at least one child <18 years were recruited from three existing Dutch cohorts. Participation included SARS-CoV-2 screening at 4-6 weeks intervals for all household members during 23 weeks of follow-up and active reporting of new onset respiratory symptoms until July 1st 2021. Follow-up was temporarily intensified following new onset respiratory symptoms in a household member or a SARS-CoV-2 positive screening test and included daily symptom recording, repeated PCR testing (nose-throat, saliva and fecal samples) and SARS-CoV-2 antibody measurement (paired dried blood spots) in all household members. Age-stratified incidence rates for SARS-CoV-2 positive and negative episodes were calculated. Symptomatology and disease burden of respiratory episodes were compared by SARS-CoV-2 status and age. RESULTSIn total 307 households were enrolled including 1209 subjects. We detected 64 SARS-CoV-2 positive and 118 SARS-CoV-2 negative respiratory outbreaks. The highest incidence rate was found in children <12 years for SARS-CoV-2 negative episodes (0.93/ person-year (PY); 95%CI: 0.88-0.96). The SARS-CoV-2 incidence in this age-group was 0.21/PY for confirmed only, and 0.41/PY if probable cases were included. SARS-CoV-2 incidence did not differ by age group (p>0.27). Nasal congestion/runny nose, with or without cough and fatigue were the three most prevalent symptom clusters for both SARS-CoV-2 positive and negative respiratory episodes. Among children, no differences were observed in the symptomatology and severity of SARS-CoV-2 positive versus negative respiratory episodes, whereas among adults, SARS-CoV-2 positive episodes had a higher number and severity of symptoms and with a longer duration p<0.001). CONCLUSIONUsing active, longitudinal household follow up, we detected a high incidence rate of SARS-CoV-2 infections in children that was similar to adults. The findings suggest that after 20 months of COVID-19 pandemic, up to 2/3 of Dutch children < 12 years have been infected with SARS-CoV-2. Symptomatology and disease severity of SARS-CoV-2 in children is similar to respiratory illness from other causes. In adults, SARS-COV-2 positive episodes are characterized by more and prolonged symptoms, and higher severity. These findings may assist decisions on COVID-19 policies targeting children.