Credit…Brandon Thibodeaux for The New York Times

The Food and Drug Administration has formally restricted the use of antibody treatments that lost their once-considerable effect when faced with the Omicron variant, pausing a therapy that had been widely embraced, including by people who eschewed vaccinations.

Many health systems stopped using the antibody treatments weeks ago as Omicron surged. And while doctors have welcomed the news of additional treatments like antiviral pills, they say the trickle of pills and other treatments are no match for the geyser of new cases.

The F.D.A. said on Monday that it was limiting the emergency use authorizations of the Regeneron and…