ABSTRACT
OBJECTIVES: Determine if a school-based Test-to-Stay (TTS) program designed to minimize learning loss reduced the incidence of COVID-19 in a US primary school district. STUDY DESIGN: Observational, simple summary analysis of attendance and effectiveness of a TTS program implemented in a California school district. METHODS: Retrospective analysis of nested medical and demographic data. Survival curves were plotted using a cumulative hazard function to compare the probability of infection among close contacts exposed at school at different points of time between participants who participated in TTS versus those who did not participate in TTS. A Cox proportional hazards regression model with time-dependent covariates was used to estimate the association of TTS status with the incidence of SARS-CoV-2 infection. RESULTS: Univariate Cox regression analysis revealed that after adjustment, enrollment in TTS was negatively correlated with the risk of SARS-CoV-2 infection (hazard ratio 0.096; 95% confidence interval [CI], 0.024-0.390; P < 0.001). CONCLUSIONS: TTS is an effective component of a layered protection strategy to prevent COVID-19 transmission in schools and communities, while minimizing the loss of in-person instruction in primary schools.