A federal judge on Monday temporarily blocked the Biden administration’s coronavirus vaccine mandate for health care workers in the 10 states that had filed a lawsuit against the government this month.

The mandate requires all 17 million health care workers in Medicare- and Medicaid-certified medical facilities, which receive government funding, to be fully vaccinated against the coronavirus by Jan. 4.

The injunction, issued by Judge Matthew Schelp of the U.S. District Court for the Eastern District of Missouri, prevents the Centers for Medicare and Medicaid Services from enforcing the mandate while the case is in court.

The judge said in his ruling that the plaintiffs were likely to succeed on the merits of the case in part because Congress had not granted the agency authority to issue a vaccine mandate.

“C.M.S. seeks to overtake an area of traditional state authority by imposing an unprecedented demand to federally dictate the private medical decisions of millions of Americans,” wrote Judge Schelp, who was nominated by President Donald J. Trump. “Such action challenges traditional notions of federalism.”

The lawsuit was filed by the states of Alaska, Arkansas, Iowa, Kansas, Missouri, New Hampshire, Nebraska, North Dakota, South Dakota and Wyoming. It said that by prompting health care workers to leave their jobs if they did not want to get vaccinated, the mandate could “exacerbate an alarming shortage of health care workers, particularly in rural communities, that has already reached a boiling point.”

Judge Schelp’s ruling is the second setback this month for the Biden administration’s vaccine mandates.

A three-judge panel in New Orleans affirmed a federal appeals court’s decision to temporarily block a requirement that companies with at least 100 employees test their unvaccinated workers weekly beginning in January. The judges said the mere existence of the regulation had resulted in “untold economic upheaval in recent months.”

“The public interest is also served by maintaining our constitutional structure and maintaining the liberty of individuals to make intensely personal decisions according to their own convictions,” wrote Judge Kurt D. Engelhardt, a Trump appointee.