While 21 states and the District of Columbia have already mandated vaccines for health care workers, six — Texas, Montana, Arkansas, Indiana, Tennessee and Georgia — implemented bans that prohibited some employers from requiring vaccines. Eighteen states had no requirement for health care workers, while five, including Utah, Arizona and Michigan, exempted health care organizations from bans on vaccine requirements.

The Supreme Court ruling covered two dozen states that had been the subject of federal injunctions that prohibited the Centers for Medicare & Medicaid Services from imposing a mandate. About 10 million workers at approximately 76,000 health care facilities, including hospitals and long-term care facilities, are affected by the requirement.

In Florida, Gov. Ron DeSantis called the new federal policy “insane” at a news conference on Thursday. The state’s Agency for Health Care Administration also indicated it would not survey health care facilities about compliance of the vaccine mandate. On Friday, Mr. DeSantis reiterated his position, posting on Twitter that Florida will reject federal mandates, “which are rooted in political, not medical science.”

Still, federal laws ordinarily displace, or “pre-empt,” contrary state and local ones, and in allowing the mandate for health care workers, the Supreme Court at least implicitly ruled that it overrode state laws banning vaccination requirements at facilities participating in the Medicaid and Medicare programs.

The specter of potentially losing federal funding if they do not comply has already persuaded some hospital chains to require vaccinations for workers who did not qualify for a medical or religious exemption.

“If we do not comply with the CMS mandate, we could compromise our ability to serve our communities and provide care to patients under the Medicare and Medicaid programs,” a spokesman for HCA said in a statement. The system, which employs about 275,000 workers, said more than 90 percent of its workers were vaccinated or had qualified for an exemption.