A peak in coronavirus infections likely has occurred in Minnesota, but Mayo Clinic forecasters warned Wednesday that the state's fifth pandemic wave is far from over.
Mayo's updated modeling predicted a peak in Minnesota's confirmed COVID-19 cases on Jan. 29, but the lag in reporting infections means that viral spread is already declining, said Curtis Storlie, a co-creator of Mayo's predictive COVID-19 model and 14-day forecast.
"We're likely at peak, reaching peak," Storlie said. "What does that mean? It means we're half done with this current surge. It's important to recognize the omicron surge is not over. There's going to be thousands of infections and hospitalizations on the way back down, too."
The prediction matches with sewage sampling at water treatment plants indicating an 80% decline in viral levels in the Twin Cities this month and declines in south-central Minnesota as well. The U.S. COVID-19 Forecast Hub also has combined multiple models into an Ensemble forecast that predicts a leveling of infection numbers this week in Minnesota, which will join the majority of states that had earlier waves of the fast-spreading omicron coronavirus variant.
"It is pretty clear that every state, their growth rate started high and it's slowing," said Nicholas Reich, director of the hub and a biostatistician at the University of Massachusetts at Amherst. "The pattern in which it slowed has been really consistent across states."
Mayo and UMass officials provided modeling updates on Wednesday as the Minnesota Department of Health reported another 52 COVID-19 deaths and 15,572 coronavirus infections. While 82% of Minnesota's 11,282 COVID-19 deaths have taken place among seniors, Wednesday's report included Carver and Cook county residents in their 30s and a Dakota County resident aged 25-29.
Minnesota for the second consecutive day reported a decline in the positivity rate of COVID-19 testing to 22.9% in the seven-day period ending Jan. 15. The rate of tests performed also began to decline, an indicator the declining rate isn't because of more people seeking to know if they are infected.
COVID-19 hospitalizations in Minnesota increased slightly to 1,553 on Tuesday, but fewer than 15% of those patients required intensive care. That is a lower rate than in other pandemic waves over the past two years.
"The severity of illness overall is clearly less with omicron compared with delta and other variants, and clearly that is impacted by vaccinations and boosters," said Dr. Conor Loftus, chairman of Mayo's outpatient practice.
Hospital systems continued to report unvaccinated patients were more likely to need intensive care and ventilators. Among 405 patients with COVID-19 admitted to Allina Health hospitals Tuesday, 56% were unvaccinated while 28% were vaccinated without booster doses and 16% had received boosters. Among the 46 patients on ventilators, 38 were unvaccinated.
Minnesota ranks 17th among states with almost 67% of its population vaccinated with the initial one- or two-dose series, according to the Centers for Disease Control and Prevention. The state also ranks second on boosters, with nearly 53% of its fully vaccinated residents having received one.
Storlie said vaccination rates influence COVID-19 modeling predictions for states, and he urged Minnesota to get its share of fully vaccinated residents with boosters above 70% to reduce the chance of another severe pandemic wave.
"It'll be Groundhog Day" if the booster rate doesn't improve, he predicted. "We're going to keep seeing this evolution, this cycle. Will it ever be as bad as this surge? Hopefully not. But if we don't want to take ahold of this opportunity that we have, that science has given us … we're going to see another surge."
Gov. Tim Walz has frequently consulted with the Mayo modelers in weighing strategies to respond to the pandemic. Storlie said the model remained fairly accurate during the delta wave last year, and some tweaks to its assumptions allowed it to be predictive during the transition to omicron.
Minnesota's peak infection rate in the latest wave has fallen below Mayo's predictions, but Storlie said that could be because many Minnesotans are discovering infections through home tests that aren't included in the state's count.
Reich said he has become less confident in forecasts of case numbers because they can be affected by delays in the reporting of test results. Ensemble's four-week case forecasts had been published on the CDC website until they proved unreliable last fall during the delta wave, he said.
Daily reporting by hospitals of COVID-19 admissions offers much more stable data for predictions, he said. While increases in COVID-19 hospitalizations have come shortly after increases in infections, the gap in time isn't as broad as once thought, he added.
Ensemble predicts little change in COVID-19 hospitalizations in Minnesota in early February, but deaths will continue to increase until Feb. 12. The models can't predict whether a new coronavirus variant will emerge and create the next wave.
"I'm sort of optimistic that we're going to be done with omicron soon … That's very different from saying we're done with COVID," he said. "What comes next is so up in the air in terms of how transmissible a new variant is, how severe it is. There are so many unknowns."
