COVID report card: How the virus spread through WA schools this year

Jun. 17—Over 1,500 COVID-19 outbreaks were tied to Washington's K-12 schools during the 2021-22 academic year, according to a state Department of Health report on how the virus moved through campuses.

These outbreaks, recorded between Aug. 1 and April 30, were associated with nearly 11,000 coronavirus cases in the state. An outbreak is defined as three linked cases or 10% of students, teachers or staff within a group like a classroom or a school-sponsored extracurricular activity.

About 90% of COVID cases tied to school outbreaks were among students, the majority 13 and younger. The median age was 14.

Vaccination rates for these age groups are the lowest. Though children ages 5-11 became eligible for the vaccine in October, less than a third (32%) were fully vaccinated as of Saturday, according to DOH data. For the 12-15 age group, 54% were fully vaccinated.

With elementary students more likely to stay with their class throughout the day, DOH said clusters are easier to identify without an intensive investigation.

It becomes more challenging for middle schools and high schools, as students move between classes and access a wider array of activities — making it harder to confirm links.

Older students, DOH said, also may have more ability to consistently wear well-fitting masks.

Where school outbreaks occurred

Though King County schools recorded the most outbreaks in Washington, the size of outbreaks in Snohomish County schools were the largest.

A whopping 7,116 cases were tied to Snohomish schools, affecting 71% of schools in the county.

King, Snohomish and Grays Harbor counties reported the highest number of public school building closures.

A majority of the outbreaks were reported in public schools — accounting for nearly 30% of all Washington public schools.

Over the school year, this led to 77 reported school building closures and a temporary return to remote learning, according to data from the state Office of Superintendent of Public Instruction.

Though private schools reported fewer COVID outbreaks, a significant 20% in the state were affected. It is not clear how many of these led to temporary school closures as private schools are not required to report this to OSPI.

DOH said the partnership between public schools and local health jurisdictions allows for more accurate reporting of outbreaks. There is not enough data to determine with certainty whether public schools were impacted more than private schools.

Where COVID spread on campus

The classroom was the primary location for transmission in schools. Less than 1% of outbreaks were linked to cafeterias, where students were more likely to be unmasked.

But identifying the precise setting of transmission is difficult, DOH said, particularly in locations with a frequent flow of people, like a lunchroom or hallway.

"Children and youth who share classrooms may share lunch as well. Additionally, the number of outbreaks occurring in K-12 schools makes it challenging for every outbreak to be investigated in detail," the DOH said.

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