Thousands of Minnesota employers have just weeks to comply with federal rules calling on workers to undergo COVID-19 vaccination or get tested weekly to fight the spread of the pandemic virus.

The rules weren't a surprise, but Thursday's announcement set the timeline and specified that employers won't have to cover testing costs.

Companies with 100 or more employees must ensure all their workers are fully vaccinated by Jan. 4, at which point those who are not must wear masks and undergo weekly testing, the Occupational Safety and Health Administration (OSHA) said.

Also on Thursday, the agency that runs the federal Medicare program announced separate vaccine mandate requirements, which don't allow a testing option, for hospitals and long-term care providers that receive funding from federal health programs.

"Vaccination is the single best pathway out of this pandemic," President Joe Biden said in a statement. "And while I would have much preferred that requirements not become necessary, too many people remain unvaccinated for us to get out of this pandemic for good."

OSHA projected that the standards will save more than 6,500 worker lives and prevent more than 250,000 hospitalizations over the next six months.

Businesses in Minnesota are left with hard decisions to make in the coming weeks, employment law attorneys say. Employers aren't exactly sure how OSHA will impose penalties of nearly $14,000 per violation and, more broadly, are worried about how mandates will affect a labor market that's already "too tight," said Vicki Stute, a vice president with the Minnesota Chamber of Commerce.

"I think there's a number of companies that have concerns [and] believe that the emergency temporary standards will create additional economic uncertainty for their companies specifically, as well as the economy as a whole," Stute said.

Last year, there were 4,796 employers in Minnesota with 100 or more workers, according to the state Department of Employment and Economic Development, that collectively account for more than 1.4 million Minnesotans.

Employers that already have high numbers of vaccinated workers might simply opt for mandating immunizations rather than go through the administrative challenges with testing. Others with many vaccine-averse employees may find it necessary to allow testing rather than risk losing workers with a vaccination mandate.

Some companies will also be forced to act despite deep reluctance to get involved in personal health care decisions — a topic that has become highly politicized, as well.

"It is causing a lot of heartburn," said Sara Sidwell, an employment law attorney with Maslon LLP in Minneapolis. "It's a fairly accelerated timeline, and there are obviously administrative and operational challenges and costs associated with both options."

Separately, the standards announced Thursday by the Centers for Medicare and Medicaid Services (CMS) apply to about 38,000 nursing facility employees across the state and more than 127,000 employees at hospitals represented by the Minnesota Hospital Association.

A trade group for long-term care providers in Minnesota sounded the alarm that the mandate could drive out health care workers and exacerbate shortages.

While OSHA's standards allow medium and large employers to provide workers with a test-out option to avoid vaccination, that's not the case for facilities accepting payment from the government's Medicare and Medicaid health insurance programs, said Patti Cullen, the president and chief executive of Care Providers of Minnesota.

"Let's be clear — this is a potential powder keg with a short fuse," Cullen wrote in an email. "We may face a scenario where we don't have enough workers to serve the seniors in our settings. And despite our pleas for help, there are no concrete solutions — either at the state or federal levels — to help us solve our unprecedented workforce crisis."

Workers can seek exemptions for medical and religious reasons. Since mandates don't apply to those who telework from home, the rules could affect return-to-work plans, said Stute, of the Minnesota Chamber of Commerce.

"The question is: Will companies continue to keep their workers then at home?" she said, noting the potential economic hit to regional downtown centers.

Employers must require each vaccinated employee to provide acceptable proof of vaccination and maintain a roster of each employee's vaccination status, said Jessica Roe, an employment defense attorney in Minneapolis. The OSHA standards require employers to provide paid time to workers for getting vaccinations and paid leave to recover from any side effects.

If employers provide the testing option, they must maintain a record of each test result, Roe said. It makes sense, she added, for those employers to help workers find testing options and consider whether it's more convenient to provide testing at the workplace.

The OSHA standards specify that unvaccinated employees who don't qualify for exemptions must wear a face covering in the workplace, Roe said, subject to exception under very limited circumstances. This will be an "enormous issue" for employers, she said, because they've been relying on an honor system when it comes to masking for workers coming back to the office.

"If you're an employee that can't or doesn't want to comply with the [OSHA] requirement of vaccine or testing," Roe said, "you may decide to look for a job at an employer with less than 100 employees."

Large employers in Minnesota, including Target and U.S. Bank, were still reviewing the new rules Thursday. Mayo Clinic, the state's largest employer, announced in October that vaccinations would be required for all workers, although staff could seek medical or religious exemptions.

"Making COVID-19 vaccination a requirement to work at Mayo Clinic will help ensure we have a healthy workforce and that Mayo Clinic is a safe place to receive care — just as our patients expect," the clinic said in a statement. About 89% of all Mayo employees are vaccinated.

Minnesota has its own agency for worker safety that must adopt the OSHA standards announced Thursday or develop an equivalent set of rules. Employment law attorneys said they expect the state will follow the federal standard.