The U.S. Food and Drug Administration Monday rescinded its authorization for Covid-19 monoclonal antibody treatments made by Regeneron Pharmaceuticals and Eli Lilly after those treatments proved ineffective against the omicron variant, over a month after some hospitals voluntarily decided to stop offering the drugs. Monoclonal antibody treatments can prevent serious illness or hospitalization among high-risk Covid-19 patients by reinforcing the body’s natural immune response. Though Regeneron and Eli Lilly’s treatments worked against previous variants of the virus, omicron’s mutation in a spike protein targeted by the treatments all but eliminated their effectiveness. Over a month prior to the FDA’s Monday...