The Food and Drug Administration's full approval Monday for Pfizer's COVID-19 vaccine sets the stage for employers across Minnesota to push harder for workers to get immunized.

Even before the regulatory action, immunization mandates were possible, attorneys say, so long as companies, universities and local governments provided exemptions to workers with religious or medical objections.

In Minnesota, several large health systems started announcing mandates and related policies in July — moves that were seen as more aggressive than the vaccination incentives that became commonplace by late spring at workplaces across the state.

FDA approval could open the door to more requirements because it lowers the litigation risk with mandating immunizations, said Susan Ellingstad, an attorney in Minneapolis with Lockridge Grindal Nauen P.L.L.P. What's more, regulatory approval likely will factor into "nonlegal calculations," Ellingstad said, that ultimately could result in more employers mandating or forcefully advocating for vaccinations.

"In addition to legal risk assessment, full FDA approval should help employers with the employee morale issues around vaccine requirements," Ellingstad wrote Monday in a note to clients. "No employer wants to tell its employees what to do, much less risk losing employees in a tight labor market."

Pfizer said the U.S. is the first country to grant full approval of its vaccine, in a process that required a 360,000-page application and rigorous inspections. Never before has the FDA had so much evidence to judge a shot's safety.

More than 200 million Pfizer doses have been administered in the U.S. under emergency provisions since December.

Leaders at the Minneapolis law firm Robins Kaplan heard overwhelming support this summer from employees after announcing a mandate for attorneys and staff to get vaccinated against COVID-19.

Even so, a few voiced concerns that the vaccine had been approved by federal regulators only for emergency use, said Ron Schutz, chairman of the firm's executive board.

"So, I'm hoping that anybody who was unvaccinated and was sitting on the fence for this reason — I'm hoping that this helps," Schutz said.

The University of Minnesota's vaccination mandate for students, which was contingent on full FDA approval of a vaccine, officially took effect Monday. It applies to the roughly 60,000 students attending the U's Twin Cities, Duluth, Rochester, Crookston and Morris campuses.

Beginning Tuesday, faculty and staff at the U must report their vaccine status. Unvaccinated workers must commit to regular COVID-19 testing, the university says. The FDA approval "marks a key milestone in managing this pandemic," U President Joan Gabel said in a message to students Monday.

Mandates from other employers will come quickly, predicted Michael Osterholm, director of the U's Center for Infectious Disease Research and Policy.

"I think many organizations believed that it would be important from both an ethical standpoint and, in some cases, a legal standpoint, to actually have a fully licensed product if they were going to mandate it," Osterholm said. "That's what's happened now."

United, Hawaiian and Frontier airlines earlier this month announced all employees must soon be vaccinated, with certain exemptions available.

Delta Air Lines, the dominant carrier at Minneapolis-St. Paul International Airport, requires just its new hires to be vaccinated. Twin Cities-based Sun Country doesn't require its employees to be vaccinated, "but we are encouraging it," a spokeswoman said.

The FDA's full approval likely won't change anything for passengers in the near term.

"The airlines are reluctant to be in a position to mandate customer behavior. They're even reluctant in some cases to mandate their own employees' behavior," said Bob Mann, an airline industry consultant.

A Delta spokesman on Monday called their vaccine stance "status quo."

The Minnesota Department of Education says that decisions around vaccine mandates for educators and school staff are made at the local level.

A school board discussion about vaccines this month at St. Paul Public Schools didn't focus on FDA approval when one school board member suggested administrators raise the possibility of a mandate with the district's bargaining units. It's unclear whether a majority of board members in St. Paul would back a vaccine requirement.

Minneapolis Mayor Jacob Frey said the city has considered mandating COVID-19 vaccines for its employees. But, he added, "We are generally moving in the direction of further and strongly incentivizing vaccination."

In St. Paul, the City Council passed a resolution last week recommending that the city "explore" a vaccination requirement for all city employees. Mayor Melvin Carter also has directed city staff to explore the idea.

Medical device manufacturer Medtronic, which has its operational headquarters in Fridley, announced last week that workers would need to be vaccinated or have a recent negative COVID-19 test result in order to enter U.S. offices starting Sept. 30.

Nothing in the federal law enforced by the FDA prohibits an employer from requiring vaccines distributed under an emergency use authorization, Ellingstad said. Nonetheless, she noted how the vaccine's emergency use authorization has been cited in lawsuits challenging mandates.

Even though employers have successfully defended their mandates in court, "the FDA's grant of full approval to the Pfizer vaccine today will be significant for many businesses not anxious to become embroiled in expensive litigation," she wrote.

Full approval should help with workers' fears over the vaccines, Ellingstad said, giving employers a fresh chance to talk with employees about the importance of immunization.

"Voluntary compliance is always better than forced compliance," Ellingstad wrote, "but as employers seek to bring people back to the workplace they are realizing a fully vaccinated workforce, however they get there, is key."

Staff writers Ryan Faircloth, Katie Galioto, Erin Golden, Anthony Lonetree, Liz Navratil and Kristen Painter and the Associated Press contributed to this report.