Breakthrough infections are an increasing part of a prolonged COVID-19 pandemic wave in Minnesota, according to new data released Friday, but people who are unvaccinated still face the biggest risk and take up more hospital beds.

Detailed breakthrough data showed that fully vaccinated Minnesotans made up 197 of the 483 deaths from Sept. 5-Oct. 9 and 1,082 of the 3,492 COVID-19 hospitalizations. With 41% of the COVID-19 deaths in that time among the vaccinated, that is an increase from 29% over the previous four months.

The trend underscores the waning immunity in Minnesotans who received COVID-19 vaccine six or more months ago — with the majority of breakthrough deaths being in the elderly and people with underlying health conditions who were prioritized for the first doses of vaccine.

"It's fair to say we are kind of in a perfect storm moment," said Kris Ehresmann, state infectious disease director. "We have delta as the dominant strain, so that certainly has changed the landscape since we first identified it in Minnesota in June. Then you do have the impact of waning immunity."

Boosters are recommended for all recipients of Johnson & Johnson COVID-19 vaccine and for recipients of the Moderna and Pfizer vaccine who are seniors or younger adults with health problems or workplace risks for viral exposure.

Minnesota has released the date of every COVID-19 positive test, hospital admission and death, but hesitated to provide similar details with breakthrough infections for fear they would be misconstrued and undercut vaccination progress.

More than 3.7 million people in Minnesota have received at least first doses of COVID-19 vaccine, or 66% of the population, leaving 2 million unvaccinated people. That includes about 500,000 children 5-11 who became eligible for pediatric COVID-19 vaccine doses last week, as well as children younger than 5 who aren't eligible.

Unvaccinated people make up 33% of the population but 63% of the coronavirus infections Sept. 5-Oct. 9, according to new state data. Seniors were 17 times more likely to be hospitalized with COVID-19 and 19 times more likely to die of the infectious disease in September if they weren't vaccinated, Ehresmann said.

Hospital leaders implored unvaccinated people to seek COVID-19 vaccine and adults to seek boosters as recommended to address a worsening bed crisis.

COVID-19 hospitalizations increased to 1,245 on Thursday and combined with non-COVID cases to fill 8,219 inpatient beds in Minnesota. While Minnesota reached a single-day record of 1,864 COVID-19 hospitalizations last Nov. 29 — before a vaccine was available — there were only 6,991 total patients admitted on that date.

"We're above 100%," said Dr. Mark Sannes, who is leading the COVID-19 response for HealthPartners, which includes Regions Hospital in St. Paul and Methodist Hospital in St. Louis Park. "We have patients who are admitted to the hospital and have no bed who are boarded in our emergency center. We're having to manage them entirely in our emergency department."

One-third of the 447 COVID-19 patients admitted to HealthPartners hospitals in Minnesota and western Wisconsin over the past 30 days have been vaccinated. Among the 48 patients who needed ventilators to maintain adequate oxygen intake, 13 were vaccinated.

"The message cannot be that the vaccine is not working, because that is false," Sannes said. "This vaccine is keeping people out of the hospital."

Minnesota has the sixth-highest rate of new coronavirus infections, according to the Centers for Disease Control and Prevention. The state on Friday reported a 9.5% COVID-19 test positivity rate, another 4,849 corona­virus infections and 28 deaths. The state's pandemic totals are 841,625 infections and 8,996 deaths.

A few other states are providing breakthrough infections by date, and all of them are showing higher rates in the unvaccinated. California reported 245 COVID-19 deaths among vaccinated people in October and 1,271 deaths among the unvaccinated.

Breakthrough cases are a problem with any vaccine and infectious disease, but studies continue to show the COVID-19 vaccine remains highly protective against severe illness and death, Ehresmann said. Breakthrough infections are rising in long-term care facilities, but the death rates are not as severe as they were in previous pandemic waves.

"If my dream came true and 100% of Minnesotans were vaccinated, then all of our cases would be vaccine breakthroughs," she said. "No vaccine is 100%."

Minnesota's vaccinated population is at risk from waning immunity because it includes people who are older and have underlying health problems or high-risk jobs for viral exposure. Ehresmann said that makes the elevated rates of COVID-19 death and hospitalization more troubling in a younger and healthier unvaccinated population.

Vaccines take a couple of weeks to produce strong immune responses, so shots won't have an immediate impact on the current "COVID blizzard" of infections, Ehresmann said. She encouraged people to wear masks, practice social distancing and seek routine testing as they return to more indoor activities and plan for holiday gatherings.

Jeremy Olson • 612-673-7744