Safety of SARS-CoV-2 test-to-stay in daycare: a regression discontinuity in time analysis

Background and ObjectivesTest-to-stay concepts apply serial testing of children in daycare after exposure to SARS-CoV-2 without use of quarantine. This study aims to assess safety of a test-to-stay screening in daycare facilities. Methods714 daycare facilities and approximately 50,000 children [≤]6 years in Cologne, Germany participated in a SARS-CoV-2 Pool-PCR screening from March 2021 to April 2022. The screening initially comprised post-exposure quarantine and was adapted to a test-to-stay approach during its course. To assess safety of the test-to-stay approach, we explored potential changes in frequencies of infections among children following the adaptation to the test-to-stay approach by applying regression discontinuity in time (RDiT) analyses. To this end, PCR-test data were linked with routinely collected data on reported infections in children and analyzed using ordinary least squares regressions. Results219,885 Pool-PCRs and 352,305 Single-PCRs were performed. 6,440 (2.93%) Pool-PCRs tested positive, and 17,208 infections in children were reported. We estimated that during a period of 30 weeks, the test-to-stay concept avoided between 7 and 20 days of quarantine per eligible daycare child. RDiT revealed a 26% reduction (Exp. Coef: 0.74, CI:0.52;1.06) in infection frequency among children and indicated no significant increase attributable to the test-to-stay approach. This result was not sensitive to adjustments for 7-day incidence, season, SARS-CoV-2 variant, and socioeconomic status. ConclusionOur analyses provide evidence that suggest safety of the test-to-stay approach compared to traditional quarantine measures. This approach offers a promising option to avoid use of quarantine after exposure to respiratory pathogens in daycare settings.