Appointments for COVID-19 tests are unavailable at several free sites in the Twin Cities amid growing concern over the omicron surge of the pandemic.

Vault Health is experiencing unprecedented demand at its free state testing sites at the same time workers' coronavirus infections are hurting its capacity to collect and process tests. Spokeswoman Kate Brickman said people with at-home tests can help by using them first, ahead of the expiration date, rather than saving them and coming to test sites.

"Just as people are physically hoarding tests as demand for testing soars, people are also now hoarding test appointments," Brickman said.

Demand comes amid a stunning increase in coronavirus activity in Minnesota, which reported a record 19.1% positivity rate of diagnostic testing in the seven-day period ending Jan. 3. The state on Tuesday also reported 29,487 coronavirus infections and 28 COVID-19 deaths detected over the weekend.

Minnesota's seven-day infection rate is 46th lowest compared with other states, but mostly because of the rapid spread of the omicron variant elsewhere, according to the Centers for Disease Control and Prevention. Minnesota's infection rate is higher now than it was last fall when it had the nation's worst rate.

Omicron infections in other states and countries have produced lower rates of severe COVID-19 than earlier strains of the coronavirus, and Minnesota health officials hope that pattern will continue.

COVID-19 hospitalizations have increased in Minnesota, rising back above 1,500 for the first time in a month and reaching 1,528 on Monday. COVID-19 hospitalizations requiring intensive care have been declining for the past month, though, and reached 263 Monday.

"We're encouraged [by] the fact we're seeing hospitalizations go up and not immediately seeing ICU admissions go up," said Kris Ehresmann, state infectious disease director. But she stressed it's too soon to know if this is a blip in the data or a trend.

State health officials urged Minnesotans to seek COVID-19 vaccinations and boosters. Unvaccinated Minnesotans make up 34% of the state's population but the majority of recent infections, hospitalizations and deaths. Minneapolis-based Allina Health reported 240 of its 393 COVID-19 hospitalizations on Monday involved unvaccinated patients. Among the 59 ICU patients, 49 were unvaccinated.

Gov. Tim Walz on Tuesday announced $200 incentives and drawings for five $100,000 college scholarships to kick-start vaccination progress in the 5-11 age group. About one-third of children in that age range have received at least a first dose.

"Getting our children ... vaccinated gives them critical protection against severe illness and hospitalization from COVID-19 and helps keep them in school," Walz said.

Minnesota's rising positivity rate in recent days reflected reduced testing over the holidays. That is no longer the case. The testing rate in the seven-day period ending Jan. 3 was the highest in Minnesota since December 2020.

Vault's test scheduling site Tuesday afternoon listed ample appointments in mid-January in greater Minnesota locations such as Duluth and Winona, and a few at Roy Wilkins Auditorium in St. Paul. But no appointments were available at the Minneapolis Convention Center, a former motor vehicles building in Bloomington, or a site in Anoka opened last week to expand testing capacity.

Brickman noted that people can walk in for tests at all Vault sites other than the Minneapolis-St. Paul International Airport. She also urged people mailing in Vault home tests to use only standard packaging, because extra tape and bubble wrap is slowing down processing.

Concerns have emerged about the reliability of a startup COVID-19 testing business. The Better Business Bureau chapter for Minnesota and North Dakota joined an investigation in Illinois of the Center for COVID Control, which operates testing sites in Minneapolis, St. Paul and other locations in the state. Consumer complaints have emerged about test results being delayed or containing incorrect information, said Bao Vang, a spokeswoman for the BBB chapter.

Tracie Ferris of Rush City went to the company's site near her downtown Minneapolis office because her children had cold symptoms and she had headaches. Providing copies of her driver's license and insurance card left her unnerved, but she grew worried when promised same-day results didn't arrive. She received an e-mail with a negative test result after she stopped in the next day, but it had her gender and test date wrong.

Asked if she has confidence in the result, Ferris said, "No, not at this point. I don't."

Before the investigation, the BBB had warned about the potential for sham testing sites popping up based on complaints in several other states.

"Anytime there is scarcity of any products or services, demand is going to go up and the supply is going to be limited," Vang said. "Scammers are going to use that opportunity and take advantage of our vulnerabilities at that time."

The agency encouraged people to talk to their doctors and do consumer research before paying for COVID-19 tests. The Minnesota Hospital Association last week also urged people not to go to emergency rooms for tests because they remain overrun with patients.