COVID-19 hospitalizations have nearly doubled in the past four weeks in Minnesota, but state health officials remain encouraged that vaccinations will prevent a surge in severe illnesses and deaths.

While doctors have reported younger patients and better outcomes than in the spring and fall pandemic waves, the 411 COVID-19 cases in Minnesota hospitals on Tuesday included 102 who needed intensive care due to breathing problems or other complications. The ICU number hasn't been that high since Jan. 23.

Gov. Tim Walz offered a stay-the-course message to Minnesotans this week to continue mask-wearing and social distancing practices and to seek the first COVID-19 vaccine available to them — now that everyone 16 or older is eligible under the state's distribution plan.

"We're racing against an increase in infections," Walz said on Tuesday before being vaccinated in a public event in Eagan. "The variants are making the virus spread faster. Hospitalizations and test positivity are ticking up. The good news is serious illness and deaths still seem to be relatively flat."

The variants include a more infectious B.1.1.7 form of the coronavirus that causes COVID-19, which health officials believe is now causing 50 to 60% of new infections in Minnesota. Twelve more COVID-19 deaths and 1,660 diagnosed infections were reported Wednesday by the Minnesota Department of Health, bringing the state's pandemic totals to 6,848 deaths and 519,529 infections.

The positivity rate of COVID-19 testing rose to 5.3% — surpassing the 5% warning threshold that suggests a high level of viral transmission. Infections numbers are rising fastest in the 10 to 19 age group and in the 40 to 59 age group of parents of these teenagers, said Kris Ehresmann, state infectious disease director.

School nurses are reporting a higher "attack rate" of the virus and that more teens are suffering COVID-19 symptoms rather than just asymptomatic infections, Ehresmann said. "They are saying, quote, 'It has a different feeling this time around.' "

The difference from the variant-driven outbreak in Europe in recent months is the broader availability of vaccine by the time the variant took hold in Minnesota.

The state on Wednesday reported that 1,658,176 people in Minnesota have received COVID-19 vaccine, and 1,031,749 have completed the one- or two-dose series. At least first doses of vaccine have been administered to 38% of Minnesotans 16 and older and also to 81% of senior citizens — a key risk group that has suffered 89% of Minnesota's COVID-19 deaths. Only two COVID-19 deaths have been reported in people 19 or younger in Minnesota and both had medical or other circumstances that played a role.

"I don't think it's going to be exactly like what we saw in November because we've gotten our highest risk population protected," Ehresmann said. "So there is a bit of a buffer there."

HealthPartners reported improvements in outcomes at Regions Hospital in St. Paul and others in its system — with COVID-19 mortality dropping from more than 10% late last year to 7% in February and 2% in March. The average age of hospitalized COVID-19 patients dropped from over 63 to 58.

Vaccine eligibility was expanded on Tuesday to everyone 16 and older in Minnesota, though some medical and pharmacy providers are still prioritizing limited doses for people at elevated risk of severe COVID-19 or front-line workers at elevated risk of viral exposure.

State officials are expecting a 20% bump in next week's shipment of federally controlled vaccine to address the increased demand.

The latest COVID-19 modeling by Mayo Clinic — an influential source of guidance in Minnesota's response to the pandemic — predicts a continued escalation over the next four weeks in infections and hospitalizations across the state.

However, the model predicts a decline over the next four months as a result of increased vaccination.

"Eventually, with enough vaccinated, I suspect we will see new cases continue, but the threat to hospitals will become minuscule," said Dr. Sean Dowdy, Mayo's deputy chief value officer. "That will be an important milestone as we will not have concerns about our hospitals being overrun," he said.

"But it will be a difficult message to deliver because the virus will nevertheless continue to be dangerous to those individuals not vaccinated."

Deaths have declined substantially in the long-term care population that was prioritized for vaccine in December.

Vaccine has been offered in almost every nursing home and assisted-living facility in Minnesota. The state reported 11 deaths among residents of these facilities in the seven-day period ending March 20, compared with 286 in the week in mid-December before COVID-19 vaccinations started.

Declines in severe COVID-19 cases have been so pronounced in assisted-living facilities that the state on Wednesday announced that fully vaccinated residents could engage in meals and social activities within 6 feet of one another while still wearing masks when appropriate.

The expansion does not apply to nursing homes that serve higher-risk individuals.

Minnesota is among 32 states that had public mask-wearing mandates in effect this week, although Wisconsin's version was overruled by the Wisconsin Supreme Court on Wednesday.

Walz said there was debate among U.S. governors and White House officials in a conference call this week over the continued necessity of masks, but he said they play an important role while Minnesota pursues its goal of an 80% vaccination rate that could result in herd immunity and stifle viral spread. "I think what we're seeing is that we're going to have to have a combination of both," he said.

Thursday marks the latest roll back of COVID-19 mitigation measures in Minnesota — with large sports and entertainment venues allowed to host events with capacity restrictions and social distancing measures in place.

The next step comes April 15, when a work-from-home mandate for applicable businesses is replaced with only a recommendation to continue the practice.

Jeremy Olson • 612-673-7744