Washington State Analysis: Schools are not islands: we must mitigate community transmission to reopen schools

Jamie Cohen, Dina Mistry, Cliff Kerr, Mike Famulare, and Daniel Klein 1 Reviewed by: Mandy Izzo, Jen Schripsema, and Kate Davidson Institute for Disease Modeling, Bellevue, Washington, covid@idmod.org Results as of July 13, 2020 5:00 p.m.

 What do we already know? School closures in Washington State were announced on March 12 th , 2020 and have contributed to reducing transmission of COVID-19. However, there remains uncertainty around the impact of school reopenings on overall transmission. Schools across the state (and nation) are currently considering strategies for reopening in the fall, including the use of cloth face coverings, physical distancing in schools, daily syndromic screening, and classroom or school cohorting. What does this report add? We applied our agent-based model, Covasim, to simulate specific strategies for school reopenings as well as changing transmission at workplaces and in the community. We calibrated the model to King County data provided by the Washington State Department of Health, including daily counts of the number of tests, diagnoses and deaths in 10-year age bins until June 15 th . While we fit the epidemic data well, we do not capture the more recent increase in cases that have occurred subsequent to this period. We compared six alternative strategies for school reopening, including changes in the contact structure of schools, the usage of face masks and other non-pharmaceutical interventions (NPIs), and the implementation of screening, testing and contact tracing of students and teachers. We found that school reopenings with no countermeasures may lead to a doubling of the COVID attack rate in the population over the first three months of the school year, but that a combination of mask usage, physical distancing, hygiene measures, classroom cohorting, and symptomatic screening, testing and tracing of students and teachers may be able to effectively reduce or even mitigate epidemic spread, depending upon the level of community transmission in the model. For example, if the workplace and community return to 70% of pre-COVID mobility by the time schools reopen, which we estimate represents a five percentage point increase from activity in mid-June, with ongoing testing and contact tracing, the use of masks, physical distancing, appropriate hygiene measures, classroom cohorting, and symptomatic screening in schools may be able to reduce the community-wide effective reproductive number to 1. This strategy would use 70 diagnostic COVID tests per 1,000 students over the first three months of the school term...

https://covid.idmod.org/data/Schools_are_not_islands_we_must_mitigate_community_transmission_to_reopen_schools.pdf