The U.S. Supreme Court declined Tuesday to hear an emergency appeal of a vaccine requirement imposed on Maine health care workers, the latest defeat for opponents of vaccine mandates.

It was the first time the Supreme Court weighed in on a statewide vaccine mandate. It previously rejected challenges of vaccine requirements for New York City teachers and Indiana University staff and students.

Justice Stephen Breyer rejected the emergency appeal but left the door open to try again as the clock ticks on Maine’s mandate. The state will begin enforcing it Oct. 29.

The Maine vaccine requirement that was put in place by Democratic Gov. Janet Mills requires hospital workers and nursing home workers to get vaccinated or risk losing their jobs.