Gov. Tim Walz will announce the next phase of the state's COVID-19 vaccine rollout plan Thursday, which is set to take effect after 70% of Minnesota seniors get at least one dose.

State officials expect to reach that goal by the end of March, according to Walz spokesman Teddy Tschann.

"Governor Walz is committed to giving Minnesota seniors the opportunity to be vaccinated before opening up the process more widely," Tschann said.

So far, 364,331 Minnesotans age 65 or older have gotten at least one shot. That's about 42% of the state's elderly population, according to state estimates.

The state is also vaccinating school and child-care workers, which along with the elderly became priority groups after health care workers and long-term care residents.

Once 70% of seniors get their first shot, next in line would be workers in other essential industries, including employees in manufacturing, grocery stores, agriculture, police and fire, the postal service and public transit.

Altogether, there are about 430,000 Minnesotans in those professions, according to state estimates. People with pre-existing health conditions that make them susceptible to serious COVID-19 complications, including hospitalization and death, are also part of the next phase.

"That's where we're intending to go," Minnesota Health Commissioner Jan Malcolm told the Star Tribune earlier this week.

Depending on which medical conditions would qualify for vaccination priority, 1 million to 2 million more Minnesotans could become eligible. About 30% of state residents are considered to be obese, one of the conditions that has been associated with COVID-19 risk.

However, some people with chronic conditions may have already qualified and received the vaccine as members of the earlier priority groups.

Because so many people are next in line to get the vaccine, the state will most likely assign priorities, putting people who are most at risk first.

That's what happened with the first rollout, where health care workers who cared for COVID-19 patients and nursing home residents, who tend to be the most at risk, were given the highest priority. Other health care workers and assisted-living residents got their shots later.

Malcolm said the goal would be to give essential workers and the medically vulnerable some idea as to when it would be their turn.

"The governor would like as much specificity on the numbers as we can get," she said.

It is unclear how much detail Walz plans to reveal on Thursday. "In anticipation of more vaccine arriving in Minnesota, our Health Department is building a framework to vaccinate more Minnesotans as quickly as possible the moment we have the doses to do so," Tschann said Wednesday night. "Governor Walz will walk Minnesotans through that strategy and announce the next phases of vaccine distribution tomorrow at 12:15 p.m."