The CoKids study is a prospective household study on occurrence and within household spread of SARS-CoV-2 and other respiratory infections. From August 2020 through February 2021, 307 households (1209 participants) with at least one child <18 years old were enrolled. During the first 23 weeks of follow-up, all household members were repeatedly screened for SARS-CoV-2 (nose-throat self-sampling) at four to six week intervals irrespective of symptoms and requested to active report 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.

A total of 183 respiratory outbreaks in 150 households were detected of which 63 (34.4%) were SARS-CoV-2 positive and 120 (65.6%) SARS-CoV-2 negative. Thirty households encountered two or more outbreaks of respiratory symptoms of which 12 households had both a SARS-CoV-2 positive and a SARS-CoV-2 negative outbreak. In total 157 (51%) households did not report any respiratory symptoms or SARS-CoV-2 infection during the entire follow-up.