As the omicron variant completes its sweep across the U.S., states with scarce supplies of monoclonal antibody therapies continue to use two treatments that federal health officials warn no longer work against the highly contagious version of the virus that causes Covid-19. Determining which patients are infected with the delta vs. omicron variant is complicated, said Dr. Christian Ramers, chief of population health and an infectious disease specialist at Family Health Centers of San Diego. Federal health officials managing allocation of the monoclonal antibody therapies paused shipments of the Regeneron and Lilly treatments on Dec. 23, after laboratory tests showed they were less effective against the surging omicron variant than the delta variant.