The legal uncertainty over a federal requirement that the nation’s 17 million health care workers be vaccinated against the coronavirus has led some well-known hospital chains to drop their own mandates — at least temporarily.

The Cleveland Clinic, HCA Healthcare and Intermountain Healthcare, among others, have said they are no longer requiring employees to be vaccinated until the courts sort out whether the federal mandate can go into effect. The hospitals’ decisions were first reported by The Wall Street Journal.

The moves are likely to slow down efforts to quell the latest surge in infections, potentially worsening by holiday traveling, large gatherings indoors and the introduction of the Omicron variant. Public health officials are renewing their pleas for more people to get vaccinations and booster shots as this latest wave of Covid cases threatens to again overwhelm hospitals. Some 66,000 Americans are now hospitalized with Covid.

Suspending the localized requirements will also make it harder for hospitals to meet the federal government’s deadline of early January for vaccinating all eligible staff if the courts uphold the mandate. Federal officials are appealing a Louisiana judge’s decision to halt the rule, and the case is likely to go to the Supreme Court. The court on Monday allowed New York State’s vaccine requirement for health care workers to continue, and the justices have previously rejected challenges to other vaccine requirements.

Exactly how many hospitals are abandoning the policy is unclear. Many states, like California and New York, and local governments, like Philadelphia’s, adopted their own edicts. HCA specified that it would continue the requirement at hospitals in places where there is a state mandate.

Several large hospital groups imposed their own requirements earlier this year after experiencing a sharp rise in cases from the Delta variant. About 40 percent of the nation’s hospitals mandated vaccinations for staff members, and the Centers for Medicaid and Medicare Services, which issued the new rule, says many facilities have already succeeded in getting workers protected.

Decisions on enforcement “have varied across the board,” said Erin J. McLaughlin, a labor and employment lawyer for Buchanan, Ingersoll & Rooney. She said an equal number of her health care clients had scrapped the requirement as had continued it.

“We do not think most hospitals are changing their mandates,” the American Hospital Association, a trade group, said in a statement. “While the current C.M.S. vaccine requirement may be delayed, hospitals and health systems are not delaying their efforts to vaccinate staff,” the group said.

But the legal landscape is confusing at best, with states and local governments often running counter to the federal efforts. In Florida, where AdventHealth, HCA and UF Health Jacksonville have all paused their requirements, Gov. Ron DeSantis prohibited vaccine mandates by private employers shortly after the federal government issued its rule for health care workers.

Exactly how many health care workers still need to get vaccinated is also unclear. While a study by federal researchers found that 30 percent of hospital workers were not fully vaccinated as of mid-September, overall immunization rates have climbed in the last few months. HCA, which employs about 275,000 workers and operates in 20 states, said most of its workers were fully vaccinated, but it would not provide specifics. Neither AdventHealth nor UF Health Jacksonville would say how many of its employees were vaccinated. Unlike nursing homes, hospitals are not required to publicly report their vaccination rates.

But many hospitals insist they are continuing efforts to persuade workers. “Based on scientific evidence and what we see in our hospitals every day, Covid-19 vaccines are safe and effective at reducing both the risk of becoming infected and the level of harm in the case of a breakthrough infection,” AdventHealth said in a statement.

Hospitals “are totally committed to having their work force vaxxed,” said Chip Kahn, the chief executive of the Federation of American Hospitals, which represents for-profit chains like HCA.

Much of the opposition to the requirements is over concerns that workers who object to the vaccine will leave. Many hospital chains said departures had not been numerous, but Mr. Kahn emphasized that even a small number of resignations can be disruptive. “Those small numbers can really be a problem,” he said.

Some hospital companies said they would pursue alternatives to keep patients and employees safe. The Cleveland Clinic, which estimated that nearly 85 percent of its employees were fully vaccinated, said it was adding more measures, “including periodic testing for those providing direct clinical care.”

Hospitals that do not want to insist on immunizations are focusing on testing their employees, said Ann Marie Pettis, the president of the Association for Professionals in Infection Control and Epidemiology, which supports a mandate for health care workers. “It’s not like they are just throwing up their hands and saying it is a free-for-all,” she said.

Other hospitals already have high numbers of vaccinated workers. Intermountain, along with other Utah hospitals, is pausing its requirement and said 98 percent of its staff was already vaccinated.