Minnesota ranks second among states with 31% of vaccinated adults receiving COVID-19 booster doses, but health officials said more such shots are needed amid a lingering pandemic wave and the threat of a new viral variant.

The omicron variant found in South Africa might reach Minnesota some day, but waning immunity and the fast-spreading delta variant present risks right now for people who are unvaccinated or due for boosters, said Michael Osterholm of the University of Minnesota's Center for Infectious Disease Research and Policy.

"Every day they haven't gotten a booster they are becoming more susceptible to infection," he said.

State Health Commissioner Jan Malcolm advised people to get vaccinated, wear masks in crowds and seek testing if they experience symptoms or viral exposure. None of Minnesota's 9,382 COVID-19 deaths and 899,739 coronavirus infections has been traced to the omicron variant, but Malcolm said the state's surveillance system is looking for it through genomic sequencing of positive specimens.

"If an omicron variant infection is found in Minnesota, we will share that information as soon as possible," she said.

Another 44 COVID-19 deaths and 4,450 coronavirus infections were reported Monday in Minnesota, which has the highest seven-day rate of new infections among U.S. states. COVID-19 hospitalizations increased in Minnesota to a 2021 record of 1,467 on Friday, and included 340 people receiving intensive care.

The state is caught in a double-whammy of high infection rates among the unvaccinated and rising infection rates among the earliest COVID-19 vaccine recipients.

Immunity appears to wane six months after vaccination or prior infection, increasing the risks for elderly Minnesotans and people with underlying health problems who were prioritized for initial doses last winter.

Thirty-four of the deaths reported Monday were in seniors and 14 were in residents of long-term care facilities. The youngest death reported Monday was a Pine County resident in the 35-to-39 age range.

Minnesota on Monday reported a total of 94,671 coronavirus infections in fully vaccinated people, including 655 people who died of COVID-19. Although the breakthrough total represents only 2.9% of Minnesota's 3.3 million fully vaccinated individuals, the rate has been increasing.

Fully vaccinated people made up 43% of coronavirus infections in the week starting Oct. 24, according to the most recent weekly state breakthrough data. The 64 COVID-19 deaths among vaccinated people that week outnumbered the 53 among unvaccinated people.

Breakthrough risks prompted the Centers for Disease Control and Prevention on Monday to switch its guidance from advising that adults "may" seek boosters when eligible to stating that they "should" seek them.

Unvaccinated people make up one third of Minnesota's population and remain at the greatest risk of bad outcomes. Age-adjusted COVID-19 death and hospitalization rates in Minnesota remain more than 10 times higher in people who haven't received their shots, state health data shows.

The omicron variant has raised concerns because of how quickly it became the dominant strain in South Africa. The variant also has properties that might allow it to evade immunity, though earlier beta and gamma variants posed that threat and didn't become dominant strains in the U.S.

Alternatives to vaccination could be needed if early warnings prove true that omicron both spreads rapidly and evades immunization, said Dr. Frank Rhame, a virologist with Minneapolis-based Allina Health. "That will push that social distancing and masking stuff to the forefront if it's really breaking through vaccine."

Minnesota's rate of people who always wore masks in public reached 79% last winter, according to surveys, but fell to 10% this summer after infection levels receded and Gov. Tim Walz lifted an indoor mandate. The state's mask-wearing rate since has risen above 20%, but remains among the lowest in the nation.

One hopeful sign in Minnesota's data was a leveling off of the positivity rate of COVID-19 diagnostic testing at 10.9%, which could indicate a stable or diminishing rate of viral spread.

The impact of the holidays on infection levels is unclear though. Infection numbers rose sharply after the Thanksgiving weekend in 2020 but declined after that. Earlier this fall, a brief decline in coronavirus numbers appeared, at least partly, to be a result of decreased testing over the MEA weekend.

Osterholm said infection numbers over the next week won't be reliable indicators of long-term COVID-19 trends in Minnesota.