At least 178 schools or districts have taken up Minnesota's offer of free COVID-19 test kits for students — a demographic seeing higher pandemic infection rates and lower vaccination coverage.

The requests came in the two weeks since the Minnesota Department of Health offered saliva test kits to middle schools, high schools and sports organizations to increase surveillance of the coronavirus that causes COVID-19. Twenty clubs representing six sports have requested 1,013 kits as well.

While risks of serious illness remain low in children, Minnesota health officials are concerned that they spread SARS-CoV-2 to others who are more vulnerable. More infectious viral variants have hospitalized younger Minnesotans, though, and could present more threats to children.

"Every person COVID-19 infects is a chance for others to become sick and for the virus to mutate into new forms that could test us again," said Jan Malcolm, state health commissioner.

Mayo Clinic modeling suggests that vaccinations helped Minnesota avert a third variant-driven pandemic wave this spring that would have far exceeded the wave that clogged up hospitals late last year. Instead, the wave peaked two weeks ago and infections and hospitalizations have declined — though Minnesota on Sunday reported another seven COVID-19 deaths and 810 infections.

The state also reported that more than 2.6 million people had received at least first doses of vaccine, and that Minnesota is 435,657 shots away from a 70% vaccination rate among eligible people that could inhibit viral spread. Gov. Tim Walz has pledged to lift the state's public indoor mask mandate before July 1 if Minnesota reaches that target.

The Pfizer COVID-19 vaccine is available to teens 16 and 17 years old, but the age cutoff for the Moderna and Johnson & Johnson doses is 18. The Pfizer vaccine could be offered to children ages 12 to 15 yet this month, but Malcolm said federal approval to vaccinate children younger than that is unlikely until 2022.

Testing is viewed as a strategy to get through the school year by quickly identifying outbreaks among students and preventing them from jeopardizing in-person learning, sports, proms and graduations. It also could be used for surveillance starting next fall if the pandemic lingers.

Edina Public Schools pioneered a "Test The Nest" surveillance program for its high school and middle schools in partnership with UnitedHealth Group, offering free weekly testing of students to find infections early before they spread to others.

While uptake was low — with 377 of 4,658 students being tested since mid-March — the surveillance found one asymptomatic infection in a student who was isolated to avoid infecting others. School officials noted that the infection rate in Edina was lower than in Hennepin County in recent weeks and that student testing could have helped.

"By getting them isolated and quarantining their exposed classmates, you stop the transmission event," said Nick Kelley, the Bloomington public health administrator who helps oversee the Edina program. "That means, in the long run, you're going to have more kids in the classroom because less kids will be exposed or sick."

False positive issue

Some parents oppose the approach, though, arguing that identification of mild or asymptomatic infections results in more quarantines and school disruptions. School nurses reported no-testing pacts this school year among some varsity teams that didn't want positive results to upset their seasons.

At one point in Edina, there were 38 students in quarantine for every one student with a confirmed infection, said Nicole Schnell, of Edina Parents 4 Progress, an organization that has criticized some school COVID-19 strategies as unnecessarily restrictive.

Schnell said she supports testing advised by doctors, but that random surveillance inevitably finds mild infections that result in quarantines, learning disruptions and stress and anxiety for students.

"For me, it's not just the testing. It's the whole package of what happens after the tests," said Schnell, noting that Edina returned to in-person learning later than some neighboring school districts.

Some critics also noted the problem of false positives. Vault Health reports a 1% rate of false positives for its saliva tests that are offered for free for students. If 100 tests were performed and found six positives, that means that one of the six was likely false, causing unnecessary isolation and quarantines.

State infectious disease director Kris Ehresmann said the overall rate of false positives appears lower than 1% and that the rate is an acceptable trade-off at a time of high viral spread for quickly identifying and slowing COVID-19 outbreaks.

"With the high level of viral transmission that we're seeing right now, we feel good about this particular test," she said. "I think that given the consequences that we can see from COVID — that we have seen this whole last year with hospitalizations and deaths — we want to make sure that we're being cautious. So we're comfortable with this level of false positivity."

Student infections declining

This spring's pandemic wave was driven in part by infections among younger, unvaccinated people and included an outbreak involving a more infectious B.1.1.7 variant that spread among youth sports activities in suburban Carver County.

The state's latest weekly COVID-19 report showed a decline in infections in pre-K-12 students in the week ending April 21, but the total was still higher than in the worst week of last winter's more severe second wave.

UnitedHealth also supported surveillance at a school in Washington, D.C., that gained 90% participation because testing was required for students to be on campus.

While higher participation offers more confidence that a school is free of COVID-19, even lower participation offers protection if it identifies an infected student before symptoms emerge, said Dr. Ethan Berke, UnitedHealth's chief public health officer.

An early catch through Edina surveillance kept contact tracing to only two close contacts, he noted.

"If they're caught later, and then we find them when they are symptomatic, they've already spread it in the school enough that that's when we're seeing 20 kids out or the whole team out," he said.

Use of the free state test kits will vary by school this spring.

Hopkins Public Schools obtained 200 kits to offer voluntary testing on the same biweekly schedule as its staff testing program. Stillwater Area Public Schools has kits available for students to take home and return the next day.

Jeremy Olson • 612-673-7744