New report examines COVID-19 testing in schools


A new report modeling the spread of COVID-19 in schools shows that diagnostic testing of students and staff might not be as effective when employing phase-in and hybrid learning models to stop disease spread, but overall those strategies work almost as well as strictly-remote learning.

Released Nov. 5, the new report was the third by the Institute for Disease Modeling looking at impacts and strategies of COVID-19 in schools, this time looking at the benefit of diagnostic testing on school populations. What the modeling found is that in most scenarios, the testing for COVID-19 had a limited impact on bringing down infection rates, and appeared to affirm that using preventative measures such as masks and social distancing had a much greater impact on preventing disease spread.

During a remote press briefing that day, Institute for Disease Modeling Senior Research Manager Daniel Klein explained the modeling was based on schools in the King County area, with assumptions of a recent case rate of 75 cases per 100,000 of population in the past 14 days, a 2.5-percent positivity rate of tests and a reproductive number of about one, meaning the disease spread on average to an additional individual for every case.

The modeling looked at five scenarios for school reopening, ranging from total reopening with no preventative measures to mitigate spread of COVID-19 in place, to fully-remote learning. Klein said that the modeling showed that even remote learning was not 100-percent effective in stopping COVID-19 spread given community transmission outside of the school setting.

Though the modeling showed a variety of different testing strategies ranging from timing of tests to the type of tests used, the only significant changes in the amount of infections based on testing strategy were for full-scale reopening of buildings, both with and without preventative measures in place. Scenarios using a hybrid model where students were in school some days and learning remotely others, and another where only students from kindergarten through fifth grade were in buildings, also had similar infection rates to fully-remote learning, regardless of testing strategy.

The modeling also showed that fully reopening schools while applying preventative measures resulted in significantly lower infection rates than reopening without. The modeling showed the potential for a 30-percent infection rate in schools over a three-month period for ones that opened up completely with no countermeasures, compared to around 1.5 percent when those measures were in place. The hybrid, elementary-only and fully-remote were still lower, with about .5-percent infections expected in the same three-month period, based on the modeling.

One of the conclusions of the report was that any reopening of schools should be with consideration with the rates of community transmission, with the state as a whole seeing a greater number of new cases recently.

“When we are in a status where we are seeing a rise in cases, that’s not the ideal time to be expanding (in-person) learning,” Lacy Fehrenbach, state deputy secretary of health for COVID-19 response, said. She added that other states with higher case rates than Washington that have reopened schools appear to back up the data in the institute’s modeling, specifically for the use of countermeasures to stop spread when students are in school.

Klein said that the modeling assumed that youth were less susceptible to COVID-19 than adults, with children under 10 being the least-susceptible, something backed up by the science, Fehrenbach said.

As to COVID-19 outbreaks with current levels of school reopening, Fehrenbach said the majority had been fewer than five cases, with most of the larger outbreaks being in high-risk communities with 75 cases per 100,000 in 14 days or more. She said some of the outbreaks had been in schools that were primarily remote, with the outbreaks potentially being among staff.

The number of cases the Washington State Department of Health has linked with school outbreaks is relatively low, as Fehrenbach said there were only 110 of those cases linked to outbreaks, roughly half being school staff. She added that there could be more cases of students and staff that were single infections, which don’t fit in the department’s definition of an outbreak.

Washington State Health Officer Kathy Lofy expressed concerns over the potential for a Fall surge in COVID-19 cases which recent case rates show might be happening. She said Nov. 3 the state saw almost 1,500 new cases of the disease, the highest daily number Washington has ever reported.

Klein noted that the modeling was based on a relatively constant COVID-19 situation, not one with rapid expansion of cases such as what is being seen currently.

“The bottom line is we’re very concerned overall about the direction of this outbreak in our state,” Lofy remarked. She urged the use of preventative measures to prevent the onset of new restrictions being put in place, and the potential for overwhelming hospitals with new cases.

“We all have to double down our efforts to wear our masks, watch our distance, and really think carefully about our social gatherings,” Fehrenbach added.


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