New report shows school reopenings are closely tied to societal activity

— from State Department of Health —

OLYMPIA — Today, the Washington State Department of Health (DOH), Public Health – Seattle & King County and Institute for Disease Modeling (IDM) released a new report that shows reopening schools without taking preventative measures may lead to a significant increase of COVID-19 in the population.

Using data from King County, IDM used their agent-based model, Covasim, to simulate different scenarios and strategies for reopening schools alongside varying levels of community activity and mobility outside schools. Simulating the first three months of school term (September 1 – December 1), the report found King County schools may be able to reopen without sustained epidemic growth, but only with several countermeasures in place and if community-wide COVID-19 transmission is low. Without any countermeasures, the number of new COVID-19 cases in the county could double over the three-month period.

“Reopening schools cannot be considered in isolation – what happens outside of schools is as important as what happens inside of schools,” said Lacy Fehrenbach, DOH’s deputy secretary of health for the COVID-19 response. “The most important step we can take to reopen schools this fall is to come together to reduce spread of the virus in our communities and statewide.”

Grouping students by age, physical distancing, wearing masks and safe hygiene may be able to reduce the impact of school reopenings on transmission, but how much of an impact these measures have will depend on the level of COVID-19 transmission outside of schools. Even with countermeasures, students and staff would need to be screened for symptoms daily and both work and community mobility would need to stay below a certain threshold. “Every part of our society is connected when it comes to COVID-19,” said Dr. Jeff Duchin, health officer for Public Health – Seattle & King County. “How well we control transmission in workplaces, businesses, recreation, families and social networks are related and all impact whether we can safely reopen schools.”  

The chart below shows the combination of various countermeasures and level of reduced mobility that are necessary to keep the effective reproductive number below the critical threshold of 1 while still allowing schools to open in the fall. When the effective reproductive number is above 1, the number of COVID-19 cases will grow.

*NPI refers to non-pharmaceutical interventions, including face mask usage, physical distancing and safe hygiene practices

“This analysis demonstrates the importance of both policymakers and individuals across society working together and doing their part to reduce COVID-19 transmission – wearing masks, practicing physical distancing and continuing to let science guide policy,” said Dr. Jamie Cohen, research scientist at IDM and lead author on the report. “This is the only way we will be able to safely reopen schools in the fall.”

At a minimum, mask usage, physical distancing, safe hygiene and classroom cohorting are necessary to reopen schools. Future analysis will investigate additional strategies, such as closing schools in reaction to cases or alternative scheduling to reduce in-school contacts.