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Vaccines for everything from influenza to measles provide partial protection against COVID-19, according to new Mayo Clinic research, suggesting that parents should get children up to date on shots before school this fall, and senior citizens should schedule their vaccinations before the winter flu season.

People showed a 28% reduction in COVID-19 risk if they received the PCV13 pneumonia vaccine in the past year compared with those who didn’t, and a 43% reduction if they received the polio vaccine before travels to at-risk locations, the study showed.

While the population-based study has limitations and was posted online Tuesday without peer review, Mayo officials said there is little harm in using the results to encourage people to seek shots that are recommended anyway.

“Make sure you get your scheduled vaccines,” said Dr. Andrew Badley, an author of the study and a leader of Mayo’s COVID research task force. “Not doing so is not doing everything you can to reduce your risks.”

The recommendation comes as Minnesota leaders wrestle with the dilemma of wanting to reopen K-12 schools this fall while facing a rising rate of COVID-19 cases and hospitalizations.

Gov. Tim Walz will unveil his school reopening plan Thursday, but he made reference during a press briefing Wednesday to a “decision matrix” that will guide districts on whether to reopen with live classrooms, online sessions or a mix. The guidance is expected to give schools discretion, depending on COVID-19 levels in their communities.

“Our guiding principles are to keep our children and our staff in the buildings safe,” Walz said. “Our second goal right behind that is to get our children back in the schools, especially our littlest learners, if at all possible.”

The governor on Wednesday highlighted 4 million protective masks that are being distributed to help people comply with Minnesota’s new indoor mask mandate.

The Minnesota Department of Health on Wednesday reported nine COVID-19 deaths and 681 infections with the SARS-CoV-2 coronavirus that causes the infectious disease. That brings the state’s totals to 1,589 deaths and 52,947 known infections.

The state reported 310 people hospitalized with COVID-19, and 143 of them needing intensive care. Those are both highs for the month of July.

Cases have been increasing for weeks, initially among teenagers and young adults but now among older, higher-risk individuals who are more likely to need hospital care, said Kris Ehresmann, state infectious disease director.

“As we have feared, we are seeing our hospitalizations begin to increase and I don’t think it’s just a blip,” she said.

Pushing vaccinations

The irony of other vaccines slowing the COVID-19 spread is that they are being used at lower rates this year. Fears of infection prompted people to cancel regular checkups and vaccinations, even before the statewide 51-day shutdown that lasted until May 18.

A survey by the Minnesota Chapter of the American Academy of Pediatrics estimated a 30% to 40% decline in childhood immunizations so far during the COVID-19 pandemic.

“As back-to-school planning is underway and certain restrictions are hopefully being lifted, it is more important than ever to ensure vaccinations are up to date to protect your children and community,” said Dr. Keith Stelter, president of the Minnesota Medical Association.

Health officials are planning campaigns to increase pediatric vaccinations as well as flu shots, because of concerns that a combined surge of COVID-19 and flu cases could overrun hospitals this winter.

Mayo researchers teamed with a data-analysis company in Massachusetts called nference, and they reviewed records from 137,000 people in the Rochester area to compare COVID-19 outcomes by vaccination.

A surprising good-news finding is that every age group had a vaccine that was recommended for them and yielded a protective benefit, said Venky Soundararajan, a founder of nference, which also has partnered with Mayo on hot-spot county level tracking of COVID-19 testing data.

“There seems to be one, if not more than one, non-COVID, FDA-approved, readily available vaccine that may well have a protective effect in mitigating SARS-CoV-2 infection in each of these age cohorts,” he said.

The MMR vaccine is generally given in two doses to children before grade school. The researchers found a 3.1% COVID-19 positivity rate among 53 people who had received that vaccine in the past year and a 5.5% rate among 94 people who hadn’t. That was a 44% difference.

The COVID-19 rate was 1.57% among 190 seniors who received the geriatric flu vaccine within a year, compared to 2.1% among 257 who didn’t — a 26% protective benefit.

The research showed the most protection for people who had received vaccinations within one year, but some protection if they had received them in five years.

Some vaccines did not show a statistically measurable benefit, possibly due to the small sample sizes of some of the groups in the study and the limits of studying a population in one geographic area. The lack of benefit from the BCG tuberculosis vaccine could be due to its limited use in Rochester, Badley said.

Trained immunity

Exactly why some vaccines work even if they don’t target the SARS-CoV-2 virus is unclear, but it probably has to do with the concept of “trained immunity,” Badley said. Vaccines could prompt the immune system to become more reactive and effective.

“If you think of the immune system like your muscles,” Badley said, “you have to exercise your muscles to make them work most effectively. That essentially is what trained immunity is.”

However, the study only proved a relationship between vaccination and lower COVID-19 rates, not cause and effect. So it’s possible that people who seek up-to-date vaccinations are simply healthier or more likely to follow public health guidelines that reduce their risks.

Ehresmann encouraged people to wear face masks per the statewide mandate, and to consider their responsibilities before putting themselves in high-risk situations such as crowded bars.

Child-care workers have picked up the virus in bars and introduced it in their workplaces, she said, and the number of new infections in long-term care jumped from 40 on Tuesday to 82 on Wednesday.

Among all COVID-19 deaths in Minnesota, 76% have involved residents of long-term care facilities, who are at greater risk due to their ages or health problems. People 70 or older now represent 9% of all known COVID-19 cases in Minnesota but 80% of the state’s deaths.

Daily cases in long-term care had been pushed into the teens earlier this summer, but are increasing as workers carry the virus with them. People can be infectious 48 hours before symptom onset, Ehresmann said.

“You can’t always know if someone is infectious,” she said, “or if you yourself are infectious.”

Walz on Wednesday toured Liberty Packaging, a Brooklyn Park business that makes corrugated boxes and has helped the state manage its stockpile of 4 million disposable masks. One million masks have already been sent to local chambers of commerce so that businesses can outfit shoppers with them rather than lose sales.

Mask-wearing might be “cumbersome” but plant workers wear them for entire shifts on hot days, said Mike Fiterman, chairman of parent company Liberty Diversified International. He encouraged people to “wear these masks and socially distance so we don’t become the issue that’s going on in Florida, the issue that’s going on in Arizona.”

Staff writers Chris Snowbeck and Glenn Howatt contributed to this report.