Rochester Public Schools is expanding a COVID-19 test-to-stay approach, after a trial in three schools kept unvaccinated students in classrooms for 602 days when they otherwise would have been quarantined.

The districtwide expansion will require a stockpile of testing kits, but Superintendent Kent Pekel said the trial proved the benefits of allowing students with COVID-19 exposures to test their way into in-person classes.

"We just can't keep losing the amount of learning time we have been to kids who don't actually have COVID and may never get it," he said.

Test-to-stay has been little used but gained attention last month when the Centers for Disease Control and Prevention published studies showing it worked and guidance for schools on how to adopt it. The concept is simple: Instead of quarantining exposed students until their infection status is known, schools permit them in class as long as regular test results remain negative.

Test-to-stay is an option only for unvaccinated students, because vaccinated students already are allowed to remain in class after viral exposure.

Albert Lea Area Schools implemented the approach in November after an early fall COVID-19 outbreak disrupted the start of classes. About half its students are unvaccinated. Other districts didn't have enough supplies to pull it off until this week, when the state secured 1.8 million more rapid tests for schools.

Northfield Public Schools is launching test-to-stay this month after it received 4,000 tests. Disruptive quarantines have been most common in elementary schools, where younger students have close contact exposures while unmasked in cafeterias, Northfield Superintendent Matt Hillmann said.

"They take longer to eat," he said. "The lunch part is where the biggest risk is."

COVID-19 cases involving students who were infectious while in pre-K-12 schools remained at elevated levels before the holiday break. The Minnesota Department of Health on Thursday reported a preliminary total of 890 cases in the week ending Dec. 18 and 1,378 in the week ending Dec. 11. That is down from 3,699 in the week ending Nov. 20.

Health officials are concerned school cases could rise again because of the fast-spreading omicron variant and the lower COVID-19 vaccination rate among eligible school-age children 5 and older. Overall on Thursday, the Health Department reported 6,936 more infections and 62 COVID-19 deaths, increasing the state's pandemic totals to 1,056,236 infections and 10,733 deaths.

"The omicron virus … is spiking relatively quickly," said Gov. Tim Walz, speaking Thursday at a new free state COVID-19 testing site at the Minnesota National Guard Armory in Anoka. "The good news is it appears to be less dangerous, but the bad news is it appears to be much more contagious."

COVID-19 hospitalizations declined in late December but increased in January — reaching 1,469 on Wednesday. State officials are bracing for an extreme spike in infections and hospitalizations over the next month, but they're hopeful the omicron wave will peak as quickly as it did in South Africa, where the variant was discovered.

Genomic sequencing of a small sampling of positive infections has found 281 involving omicron in Minnesota, but preliminary analysis suggests the variant is causing 90% of new COVID-19 cases in the state.

The state expanded testing sites to help people quickly learn if they are infected and encouraged more Minnesotans to get COVID-19 vaccinations and boosters that sharply reduce the risk of severe illness, hospitalization and death.

Minnesota also received its first every-other-week shipment of the new Pfizer and Merck COVID-19 antiviral pills. The initial 3,200 doses went to providers serving the neediest patients at greatest risk for severe illness, state Health Commissioner Jan Malcolm said.

Severe COVID-19 has been less common in children throughout the pandemic. However, the rate of pediatric hospitalizations has risen nationwide since omicron replaced delta as the dominant coronavirus strain.

"Delta was primarily a lower respiratory disease," said Dr. Gregory Poland, head of Mayo Clinic's COVID-19 vaccine research group. "Omicron tends … to be more upper airway. That equates to decreased morbidity in adults who have large upper airways and is a decided negative in young kids who have narrow upper airways."

Rochester's test-to-stay trial launched in November at Harriet Bishop Elementary, Willow Creek Middle and John Marshall High schools. The district sent enough kits home with participating parents to test children for a week after viral exposure. Parents logged the test results on a website each morning to gain clearance for their children to attend class.

Results varied by school, with the option being more popular among parents with grade-school children. Seventy of 74 Harriet Bishop students accepted the test-to-stay offer, and only three tested positive, requiring them to isolate at home.

None of the elementary school's parents fell short on daily testing or reporting — which would have resulted in their children having to quarantine. The grade-school children spent 229 days in class that otherwise would have been spent in quarantine.

Most students with COVID-19 risks are identified a day or two after viral exposure, and their seven-day quarantine periods often fall across weekends, said Leah Bancroft, the district's health services coordinator. As a result, most children in the test-to-stay pilot needed to submit test results only on three mornings before class.

Bancroft said participation might decrease when the test-to-stay approach is used districtwide, because staff won't be as able to explain the benefits and encourage parents to maintain the daily reporting.

Malcolm said she supported test-to-stay programs that reduce student quarantines, though they use up a lot of tests. She added that the CDC calls for universal mask use in schools to reduce the risk of potentially infected students spreading the virus during their test-to-stay periods.

Test-to-stay programs might become easier under CDC guidance issued this week, which shortened recommended quarantine lengths to five days for asymptomatic people who then wear masks for the next five days.

Malcolm said Minnesota will follow the CDC guidance and that it applies to pre-K-12 schools. Isolation lengths for people who test positive also are being shortened from 10 days to five days for people who are asymptomatic. Negative tests are recommended to conclude the shorter quarantines or isolations but are not required, Malcolm said.

The Albert Lea district is preparing to shorten its test-to-stay and quarantine lengths to five days in response to the CDC guidance and also will provide tests to infected students on the fifth day of their isolations, Superintendent Michael Funk said. Negative test results will allow them to return to class on the sixth day, while positive results will require they remain isolated for 10 days.