COVID-19 hasn't been a once-in-a-lifetime event for Big Lake substitute teacher Rebecca Schwirtz — or for more than 8,000 Minnesotans like her who have tested positive more than once for the infectious disease.

Reinfection with the coronavirus has meant two prolonged COVID-19 illnesses, two basement isolations and two extended absences from work for Schwirtz and has made the 40-year-old mother of three paranoid about subsequent sniffles or coughs.

"Whoever is making these home COVID tests is making a killing," Schwirtz said, "because I buy them — as many as I can get."

Health officials have known of the potential for reinfections — after hopes of COVID-19 being a one-and-done illness were dashed early in the pandemic — but Minnesota for the first time on Monday quantified the problem. The state Department of Health reported a total of 8,184 reinfections, including a few people who had COVID-19 three or more times.

While reinfections make up only 1% of the 797,984 coronavirus infections reported in Minnesota, state Health Commissioner Jan Malcolm said they are proof that previous illness isn't a free pass and that vaccination is important.

"Unlike some other things, you get COVID once it doesn't necessarily mean you aren't going to get it again," she said.

Minnesota's pandemic total includes 2,857 new first-time infections reported on Monday along with 25 COVID-19 deaths.

The state's death toll increased to 8,694 — with the 424 deaths reported so far in October the highest monthly total since 775 deaths were reported in January.

The state reached a low of 55 COVID-19 deaths in July before the latest wave was fueled by the fast-spreading delta variant.

The wave prompted the Biden administration to issue a COVID-19 vaccine mandate for large employers, though federal rules have yet to be published. Many businesses pushed ahead with mandates anyway, setting deadlines by which workers could get vaccinated or file exemptions.

Minnesota's health care providers reported better than 90% vaccination rates among workers, but Duluth-based Essentia Health announced that 49 workers were dismissed for missing its Nov. 1 deadline and Minneapolis-based Allina Health reported 23 separation agreements.

HealthPartners reported that fewer than 45 full-time workers had been placed on one-month unpaid leaves, giving them final chances to get vaccinated or file exemptions. North Memorial has a Dec. 1 deadline for its workers.

While indicators of pandemic severity are below October peaks, progress has ebbed. The state reported that 908 inpatient hospital beds in Minnesota were filled on Friday with COVID-19 patients, including 214 requiring intensive care. The positivity rate of COVID-19 diagnostic testing is 7.3%, below a recent peak of 8.4% but above the state's 5% caution threshold.

The state on Monday also reported that 57,023 coronavirus infections have occurred in Minnesota's 3.2 million fully vaccinated individuals — a breakthrough infection rate of 1.8%.

The breakthrough cases included 2,609 people who were hospitalized and 372 who died of COVID-19.

Breakthrough infections accounted for about 33% of the infections identified in the past week.

Schwirtz is both a breakthrough and reinfection case.

Her first coronavirus infection came in late December, when her family celebrated after months of home confinement by going downhill skiing and eating out.

Schwirtz thought she had food poisoning but realized it must be something else because people who ate the same food were healthy.

Schwirtz recovered after two weeks of rest and minimal water and food intake and happily sought COVID-19 vaccination in February. She remained cautious when classes started this fall, going in early to sanitize rooms in which she was teaching to reduce risks for students, when she suffered allergy-like symptoms and tested positive again in early October.

This time, she felt classic flulike symptoms — with no fever but labored breathing.

"If I had to go up a flight of stairs, I was like winded when I got there and had to take a little break," she said.

The Health Department assembled reinfection statistics this fall after the Centers for Disease Control and Prevention reached a case definition, which is when a person tests positive at least 90 days after an earlier infection.

Epidemiologists will use the data to study whether variant strains increase reinfection risks and second infections produce worse illness.

Studies show that COVID-19 vaccine remains strongly protective against hospitalization and death, but has lost some effectiveness at preventing any infections.

Third booster doses of Moderna and Pfizer vaccines have been recommended for seniors and younger adults with underlying health problems or jobs that increase their infection risks.

Boosters are recommended for all Johnson & Johnson vaccine recipients.

Schwirtz said she will seek a booster as well as shots for two of her three children younger than 11 when they become eligible.

Schwirtz's story could make a case for giving up, because she tried to avoid COVID-19, followed the mitigation advice and still tested positive twice. Instead, she said she hopes it is a cautionary tale after 20 months to still take precautions and try to protect others from COVID-19 by slowing down viral spread.

"Try your hardest," she said.