Minnesota data upholds COVID-19 vaccine benefits ahead of federal booster decision

Minnesota's muddled COVID-19 breakthrough data still shows a protective benefit of vaccination for seniors, even amid declines in pandemic activity.

Thursday's state pandemic update showed that unvaccinated seniors were 2.5 times more likely over the past two months to be hospitalized for COVID-19 compared with seniors who have received initial shots plus boosters. Unvaccinated seniors were almost twice as likely to die from COVID-19 as well.

The protective benefit showed in Minnesota's data, even though some seniors received their boosters months ago and might not have much vaccine-induced immunity left. Federal health officials are expected this month to announce that seniors and others with elevated COVID-19 risks can seek additional boosters to restore immunity levels.

More booster options for high-risk individuals make sense because COVID-19 isn't seasonal like influenza and can quickly emerge in unprotected populations, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. Japan avoided widespread COVID-19 for two years but was susceptible in late 2022 to the fast-spreading omicron coronavirus variant because it hit at a time of waning immunity.

"I don't think we should wait for a seasonal approach to this," Osterholm said, "because this is not a seasonal disease yet."

April has been a pivotal month in the pandemic, when fast-spreading coronavirus variants caused brief upticks in COVID-19 in 2021 and 2022 in Minnesota before infection levels declined or leveled off for the summer. No signs of an uptick have emerged in April 2023, though.

Viral levels in wastewater slightly increased in some regions of Minnesota in late March, but they remain well below peak levels in February. The 233 COVID-19 hospitalizations in the state on Tuesday also were down from a recent peak of 633 in mid-December.

Minnesota's COVID-19 breakthrough data was most useful in fall 2021, when booster vaccine doses were first recommended to combat a severe delta variant of the coronavirus. In late November that year, the age-adjusted rate of COVID-19 hospitalizations was 40 times higher in unvaccinated Minnesotans than those who had received boosters.

In early 2023, unvaccinated non-elderly adults in Minnesota are only slightly more likely to be hospitalized with COVID-19. The lower virulence of circulating coronavirus strains could be reducing overall risks along with immunity levels from prior infections.

COVID-19 death risks have declined across all age groups as well, but not as much for seniors. They make up 83% of Minnesota's total of 14,624 COVID-19 deaths, but 93% of the 566 COVID-19 deaths reported so far in 2023.