Updates from two large Minnesota hospital systems show that fully vaccinated people make up a minority of COVID-19 hospitalizations and an even lower share of severe illness requiring intensive care and ventilators.

Minneapolis-based Allina Health reported that 176 patients were hospitalized with COVID-19 on Monday and that 40 (or 22%) were vaccinated against the coronavirus that causes the infectious disease. Sioux Falls-based Sanford Health reported 159 patients with COVID-19 hospitalized on Tuesday across its facilities in the Dakotas and Minnesota, and that 16 (or 10%) were fully vaccinated.

The hospital systems are among the first in the nation to report their COVID-19 hospitalizations by severity and vaccination status, supplementing public health data and research suggesting that vaccine remains strongly protective against severe illness.

Minnesota leaders have encouraged more vaccinations against a pandemic that has caused 8,025 COVID-19 deaths and 692,029 diagnosed coronavirus infections in the state, including 14 deaths and 1,642 infections reported Wednesday. Minnesota ranks 21st among states with a first-dose vaccination rate of 74.3% in its eligible 12 and older population, according to the Centers for Disease Control and Prevention.

"If you aren't vaccinated yet, now is the time to make a difference in the battle against COVID-19," Gov. Tim Walz said Tuesday in a news release about expanded hours at the state's Mall of America COVID-19 vaccination site.

The disparity in breakthrough hospitalization rates between the two systems could be explained by several factors. Allina's primary service area includes the Twin Cities, which has a higher vaccination rate and more potential for breakthrough infections as a result, when compared with western Minnesota and rural regions served by Sanford.

The Dakotas had some of the highest vaccination rates in the nation earlier this year as they used efficient delivery systems to hasten immunizations of health care workers, but their progress has declined. First-dose vaccination rates among people 12 and older are 70.1% in South Dakota and 60.2% in North Dakota — the latter being the fifth worst among U.S. states, according to the CDC.

Data from the two hospital systems agreed on one key trend: Hospitalized patients with breakthrough COVID-19 cases were less likely to need intensive care or ventilators. Only one of Sanford's 34 COVID-19 patients on ventilators had been fully vaccinated compared with two of Allina's 21 patients.

Several national studies with Minnesota input have found that COVID-19 vaccines are losing some effectiveness at preventing infections amid the rise of the delta variant. However, the studies have found that the vaccines remain strongly protective against severe illness, hospitalization and death.

Elderly Minnesotans have been at greater risk of severe COVID-19, making up 87% of the state's COVID-19 deaths and 12 of the deaths reported Wednesday. While the first-dose vaccination rate among seniors is nearly 95% in Minnesota, health officials said vaccines tend to produce less of an immune response in the elderly, making them at heightened risk for breakthrough infections.

Mayo Clinic's 14-day modeling forecast of COVID-19 activity predicts increases in infection rates in Minnesota — where the current rate of 39 infections per 100,000 people per day could increase to 55 by Oct. 4. Mayo modeling has shown some slowdown in the rise of COVID-19 activity, though, and Minnesota's reported positivity rate of COVID-19 diagnostic testing declined this week from 7.1% to 6.8%.

The positivity rate still remains above Minnesota's 5% caution threshold for substantial viral spread.

The CDC's latest Ensemble model, released Wednesday, predicts little change in Minnesota's infection rate through Oct. 15. Previous forecasts from Ensemble, which aggregates COVID-19 models from across the U.S., had predicted a slight decline in coronavirus activity in the state.