Minnesota Republicans are turning to natural immunity from COVID-19 as a way to push back on vaccine mandates, arguing that hospitals, businesses and public institutions should consider past infection in exempting some from requirements.

The idea is gaining traction in Republican-led legislatures around the country, despite pushback from public heath officials who say protection from infection varies dramatically from case to case. Studies show vaccines can cut the risk of infection even for those who have recovered from the virus.

But Republicans leading the Minnesota Senate say state and federal health agencies have shut down any debate, and they want natural immunity to be discussed as part of the state's pandemic response when the legislative session kicks off on Jan. 31.

"I think some of the vaccine hesitant, which have now become vaccine militant over government actions in particular, would find it an interesting conversation," said Republican Sen. Jim Abeler, chair of the Health and Human Services Policy Committee in the chamber. "Truth could take us where it leads."

Democrats in the divided Legislature are pushing back on the idea as COVID-19 cases surge to new highs in the state, triggered by the more infectious omicron variant. The GOP push bucks vaccine efforts and policies instituted by medical professionals, said House Health and Human Services Chair Tina Liebling.

"My biggest concern about the whole thing is how they are contributing to the undermining of confidence in our medical institutions and our scientific institutions," said Liebling, DFL-Rochester.

The U.S. Supreme Court recently blocked a federal mandate that would require businesses with 100 or more employees to make workers get the shot or a weekly test, although it continued a federal rule requiring vaccination for most workers in health care settings. The ruling left it up to private businesses and organization to set their own policies.

States such as Florida and Utah passed laws late last year to let workers opt out of COVID-19 mandates if they can prove immunity through a prior infection. Republicans in neighboring Wisconsin and New Hampshire are pushing similar bills at their Capitols this year.

Last month, more than three dozen Minnesota House Republicans sent a letter to the head of Mayo Clinic in Rochester, criticizing the hospital's vaccine mandate as "excessive" and asking them to consider natural immunity in providing exemption to employees and helping with workforce shortages.

Minnesota Republican governor candidate Scott Jensen, whose campaign has focused on criticism of COVID restrictions, is not vaccinated, citing his previous infection from the virus.

Republicans in control of the Senate want to add COVID-19 immunity to a state law that allows people to provide proof of immunity to exempt them from vaccine requirements for other viruses. That law, which applies to public or private higher education institutions, requires students to provide proof of immunization against the measles, rubella, mumps diphtheria and tetanus unless the student can provide a doctor's note and lab confirmation attesting that they have recovered from the disease and have naturally acquired immunity.

Republican Sen. Michelle Benson, the former chair of the chamber's health and human services finance committee and a candidate for governor, has approached other Republicans about adding a COVID exception to the law. She said tests can determine someone's level of antibodies after a COVID infection and the conversation would show lawmakers are listening to people who are hesitant about the vaccine.

"The fact of the matter is, when your body gets infected by the virus, it does have some level of immune response. When your virus gets injected with a vaccine, it does have some immune response," said the Ham Lake Republican. "If we want to talk about slowing down this disease, talking about natural immunity is a way for this administration and for the CDC to say, 'We hear your concerns.' And shutting it down keeps a barrier up between people."

But natural protection from contracting COVID is different than other viruses and varies greatly between individuals, depending on how severe their symptoms were and how long ago they were infected, said Marc Jenkins, director for the Center of Immunology at the University of Minnesota.

Tests to determine the level of antibodies someone has after infection require a blood draw and aren't widely available, he added. Scientists still are trying to determine at what level someone is technically immune from COVID, he said, while vaccines provide more consistent levels of protection.

"Natural immunity can be very potent but it can also be not so potent, and that depends on the level of the initial infection," Jenkins said. "Because of that, and in the absence of a robust antibody testing program, it's best to try and get people to very high levels of protection through vaccination."

The U.S. Centers for Disease Control and Prevention studied adults hospitalized for COVID-like sickness between January and September. They found unvaccinated adults, despite previously having coronavirus, were more than five times more likely to test positive for the virus than vaccinated people who had never had COVID before, meaning their infection didn't give them stronger protection against reinfection.

In September, a CDC report found roughly one-third of people with COVID-19 in the study had no apparent natural immunity.

Recent studies show people with some of the highest levels of protection against COVID-19 are those who contract the virus — and then get the vaccine.

"The perfect system would be one in which antibody testing was available to everybody, and that could then be used to drive clinical decisions or decisions about who has immunity or who doesn't," Jenkins said. "Without a robust antibody testing program, I think counting on natural infection as immunity is risky."