As coronavirus infections here have shot up, so has uncertainty about the virus’s trajectory in the fall and winter — and fears that opening school buildings will intensify the pandemic. 

After a new public health report suggested schools can’t open until transmission drops significantly, King County districts told parents to gear up for a school year that starts online. As of this week, more than half of Washington’s students are expected to begin the school year remotely

But what does the latest research tell us about the effectiveness of school closures? And what do federal and local officials say?

In short: federal officials are pushing schools to reopen, but the jury is still out on key questions, such as how well children spread the virus, and whether closures contain spread. 

Government guidance

In new guidelines issued last week after President Donald Trump pressured the agency to prioritize school reopening, the U.S. Centers for Disease Control and Prevention (CDC) strongly encouraged school buildings to open. The new materials emphasize the critical role of schools, and largely downplay the risks of coronavirus transmission and illness in children. The agency acknowledged that it isn’t safe to open where transmission is high — as is the case in several Washington counties.

The federal agency has revised its advice several times, based mostly on new scientific findings and updates to health and safety practices. The latest revision came after Trump sharply criticized the CDC’s earlier, more restrictive guidance. Trump also threatened to withhold funding from districts that keep buildings closed, though it’s unclear that he has the power to do so.

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Among the CDC’s latest recommendations:

  • Everyone should wear masks inside school buildings.
  • School leaders should consider sorting students into small “pods” that are kept separate from other children and school staff.
  • Schools should consider canceling after-school programs where social distancing isn’t possible.
  • Schools can move classes outside or into unused community buildings. 

Some of this advice aligned with what Washington officials recommended, though the state’s schools chief, Chris Reykdal, has said he’s primarily taking cues from state health officials — not the CDC.

In June, Reykdal said he expected most districts to reopen buildings. But following a surge in cases this summer, and a new report suggesting opening schools might trigger “exponential growth” in COVID-19, Reykdal then said he respects local decisions to hold school remotely.

Reykdal and Gov. Jay Inslee, along with State Health Officer Kathy Lofy, announced Aug. 5 that based on local levels of community transmission, it would be unsafe for most of Washington’s students to return to classrooms. But the state officials stopped short of mandating school closures or other measures.

Also in favor of reopening: a major scientific panel that recently weighed the risks to children if schools stay closed, and the American Academy of Pediatrics, which favors reopening so long as it could be done safely.

Emerging research

Researchers are still working to settle two questions: how effective children are at spreading coronavirus, and how well school closures help contain transmission.

On Wednesday, we edged a bit closer to answering the second one. Researchers published a study in the peer-reviewed Journal of the American Medical Association that suggests closing schools had dramatic effects: Closures helped save tens of thousands of lives and resulted in nearly 1.4 million fewer cases of coronavirus, the researchers found.

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But the findings come with several caveats — and warnings from researchers who caution against using the results to keep schools closed. The data comes from a period when schools weren’t taking safety precautions, such as requiring masks and social distancing, and likely wouldn’t be applicable today, when many districts plan to enforce such measures.

The research also couldn’t rule out the possibility that other factors, such as closing businesses or social-distancing rules, contribute to the results.

“The problem is that most places including Seattle closed schools very close to the time they made all these other changes,” said Dimitri Christakis, director of the Center for Child Health, Behavior and Development at Seattle Children’s Research Institute. “It’s very difficult to separate the net contribution of schools.”

Scientists probed school closure data, coronavirus incidence and mortality rates from early March, before most schools closed, until early May in all 50 states. They used a statistical analysis to look for associations between the date of school closures and daily changes in coronavirus outcomes. Closing schools was most effective in places that closed earlier than later.

Researchers are also still trying to pin down whether children carrying the coronavirus can spread it to others. On Thursday, researchers reported that infected children may carry at least as much coronavirus in their nose and throats as adults, adding heft but not definitive proof that children transmit the virus. The research follows a large South Korean study that suggests children transmit coronavirus at varying degrees depending on their age — an important factor when deciding when and how to open schools.

Children between 10 and 19 spread the virus at least as effectively as adults do, the researchers found. Younger children are less likely, but still capable of transmitting the virus.

Again, the findings aren’t definitive. The researchers, who traced the contacts of more than 5,700 people with coronavirus, only followed symptomatic people, and didn’t capture how asymptomatic children spread the illness. The researchers’ decision to group 10 year olds with teenagers also leaves unclear whether younger adolescents are as capable at spreading the virus as older peers.

“This gives us further indication there is going to be substantial transmission from at least some fraction of the 10- to 19-year-old age group, but it leaves a lot of questions,” said Carl Bergstrom, biology professor at the University of Washington.