(Reuters) – A federal appeals court on Wednesday revived in 26 U.S. states a COVID-19 mandate issued by President Joe Biden's administration requiring millions of health care workers to get vaccinated if they work in facilities that receive federal dollars.

In a rare win for Mr. Biden's pandemic strategy, a three-judge panel of the 5th U.S. Circuit Court of Appeals in New Orleans ruled that a lower court had the authority to block the mandate in only the 14 states that had sued and was wrong to impose a nationwide injunction.

The Biden administration mandate requires that health care facilities get staff vaccinated against the coronavirus or lose funding from the U.S. Centers for Medicare & Medicaid Services, which administers the two large government health care programs.

The rule initially required more than 2 million unvaccinated health care workers to be vaccinated by Dec. 6. It was blocked before the deadline and remains temporarily blocked in 24 states - the 14 states involved in the case reviewed by the 5th Circuit and 10 states where the mandate was blocked by a Nov. 29 ruling from a federal judge in St. Louis.

The 14 states that sued are: Alabama, Arizona, Georgia, Idaho, Indiana, Kentucky, Louisiana, Mississippi, Montana, Ohio, Oklahoma, South Carolina, Utah and West Virginia.

The administration argued that the mandate will potentially save thousands of lives every month, with COVID-19 cases and deaths expected to spike with the onset of winter and arrival of the fast-spreading Omicron coronavirus variant. Numerous lawsuits have been filed seeking to block vaccine mandates issued by governments and businesses as public health measures amid a pandemic that has killed more than 800,000 Americans.

The 5th Circuit ruling said the Biden administration had not made a strong showing that it was likely to prove during the litigation that it has the authority to impose the rule. The panel included Judge Leslie Southwick, appointed by Republican former President George W. Bush, and Judges James Graves and Gregg Costa, both appointed by Democratic former President Barack Obama.

The rule is one of three far-reaching Biden administration requirements aimed at boosting vaccination rates in the United States, where infections are rising and deaths remain above 1,000 per day. Republican state attorneys general and conservative organizations and businesses have challenged the rules.

In November, the 5th Circuit blocked the administration's workplace vaccine-or-testing mandate for businesses with at least 100 employees. That mandate, issued by the Occupational Safety and Health Administration, is being reviewed by the 6th U.S. Circuit Court of Appeals in Cincinnati, dominated by judges appointed by Republican presidents.

On Wednesday, the 6th Circuit sided with the Biden administration, agreeing to hear the case initially before a three-judge panel rather than all 16 active judges on the court.

Two Republican-appointed judges used their dissenting opinions from that order to spell out their opposition to OSHA's mandate, which could indicate the court is leaning toward reviving the agency's rule.

"The judges who wrote the opinions could be concerned the court is going to go the other way," said Brian Abramson, an author on vaccine law.