More than a half-million third or booster doses of COVID-19 vaccine have been administered in Minnesota to counter the latest delta wave of the pandemic and waning immunity among people who received shots months ago.

The Minnesota Department of Health in the past week identified another 7,821 breakthrough coronavirus infections among more than 3.2 million fully vaccinated people, including another 111 people who died of COVID-19 despite their immunizations. The state's breakthrough total as of Monday reached 64,844 infections — more than 2% of Minnesota's fully vaccinated population — and 483 COVID-19 deaths.

State health officials urged people to seek boosters when recommended because of the risks of waning immunity, even though the original COVID-19 vaccine doses continue to protect against severe illness, hospitalization and death. Age-adjusted rates of coronavirus infections in September were four times higher in the unvaccinated vs. the vaccinated, according to the latest state data, while rates of COVID-19 deaths were more than 15 times higher among the unvaccinated that month.

"Anyone who is eligible, including seniors, should get a booster shot as soon as they can. Our own MDH data shows how effective the vaccine is," said Kris Ehresmann, state infectious disease director.

Minnesota's pandemic totals, regardless of vaccination status, reached 819,239 infections and 8,862 COVID-19 deaths, including 4,253 infections and 34 deaths reported on Monday. The state's reported positivity rate of recent COVID-19 diagnostic testing also rose to 8.5%, a peak in 2021.

The proportion of deaths involving people younger than 65 has increased from 12% before June 1 to 26% since that time — with Monday's report including the deaths of an Itasca County resident in the 25-29 age range and a Dakota County resident in the 45-49 age range. Conversely, long-term care facility residents made up 60% of COVID-19 deaths reported before June 1, and 26% since that time.

However, state Health Commissioner Jan Malcolm said booster shot clinics are being arranged statewide to maintain protection among vulnerable long-term care residents, because immunity appears to start waning at six months and many residents received their shots much earlier than that.

"We're starting to see some really good uptake of those booster doses in long-term care," she said, "and also happy to say we're seeing some steady increases in staff vaccination rates as well."

Booster doses are recommended in Minnesota for all recipients of the single-dose Johnson & Johnson vaccine, and for recipients of the two-dose Moderna or Pfizer vaccines who are seniors or younger adults with underlying health problems or occupational risks for viral exposure. People with weakened immune systems already were recommended to receive extra doses as part of the initial vaccination series.

Minnesota's vaccine dashboard shows that 523,905 third or booster doses have been provided. However, the state database excludes vaccinations by federal agencies such as the Department of Veterans Affairs and the Indian Health Service.

Including those doses, nearly 620,000 people in Minnesota have received boosters, according to the Centers for Disease Control and Prevention. Minnesota ranks third among states, according to the latest CDC data, with boosters provided to 19.2% of vaccinated people 18 and older.

Jeremy Olson • 612-673-7744