No sign yet of holiday bump in COVID-19, flu levels in Minnesota

Infectious disease levels didn't increase over the holiday week, defying historical flu season trends and easing pressure on Minnesota's hospitals.

Hospitals had one of their busiest days in the nearly three years of the pandemic on Dec. 7, when 8,324 patients filled inpatients beds as a result of COVID-19, influenza and other health issues. That number dropped to 7,378 on Tuesday, and the number of inpatient cases involving COVID-19 dropped from 633 to 560 over those two dates.

Trends were mostly flat last week, according to state COVID-19 and influenza updates Thursday — although that could be partly due to reduced testing over the holidays.

The 168 flu-related hospitalizations identified in Minnesota the week ending Dec. 31 were only one higher than the prior week. Both represent a decline, though, from the nearly 600 hospitalizations per week during an unusual fall influenza surge in late November and early December.

Health officials warned that there are reasons for concern and caution, including the potential for a second seasonal influenza wave and the possibility of a new viral variant causing more COVID-19 again.

Sewage sampling last week at the Metropolitan Wastewater Treatment Plant in St. Paul found increases in two concerning variants, BA.2.75 and XBB, of the coronavirus that causes COVID-19. The viral load in sewage samples rose in mid-December to its highest level since May, but has dipped since then.

Any surge in the XBB variant over the next four weeks could be a sign of trouble because of the way it has fueled COVID-19 elsewhere — even in people with prior infections or vaccinations, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. For now, the relative lack of change in COVID-19 levels in Minnesota and surrounding states is itself surprising.

"This High Plains plateau just continues," he said.

Low flu and COVID-19 vaccination levels remain a concern, especially for seniors at greatest risk of severe illness from infections. The median age of Minnesota's 107 influenza-related deaths so far this season is 80.

Minnesota this week neared 14,000 COVID-19 deaths in total for the pandemic. Risks are much lower compared to the last two winters. The 179 COVID-19 deaths identified so far last month in Minnesota compared to 1,082 in December 2021 when delta and omicron variants were causing widespread severe illness.

What risk remains is concentrated among senior citizens — who made up 96% of last month's COVID-19 deaths. And while 95% of Minnesota seniors have received some COVID-19 vaccine, only 59% are considered "up to date" with recommended boosters to maintain immunity levels.

State breakthrough data shows much less difference in risk levels between the vaccinated and unvaccinated than in earlier pandemic waves. Unvaccinated seniors over the past 60 days were 3.3 times more likely to be hospitalized with COVID-19 than seniors who had received initial shots plus recommended boosters. Unvaccinated seniors had been at nearly 18 times greater risk at one point last year.

However, the state breakthrough data as currently defined could be underrepresenting the protective benefits of COVID-19 vaccine.

By definition, the boosted population in the data includes people who received their additional doses more than a year ago — and who have suffered waning immunity that puts them at heightened risk once again. Breakthrough infections rates in the up-to-date population are not available.