The US Food and Drug Administration could decide in the coming days to take steps to curb the use of antibody treatments produced by Eli Lilly and Regeneron, the source said, pointing to the growing body of evidence that shows their monoclonal therapies don't effectively neutralize the virus' Omicron variant.

The National Institutes of Health had recently updated its guidelines to advise clinics against using these treatments on patients with mild to moderate Covid-19 due to their diminished effectiveness against the Omicron variant.

This past week, senior health officials in the administration, including Dr.

Abbott himself received Regeneron's monoclonal antibody therapy treatment when he tested positive for coronavirus in August when its Delta variant was predominant.

The fast-spreading Omicron variant was first detected in the US on December 1, and quickly became the predominant variant.

The vast majority of coronavirus cases are not sequenced to determine the variant, and doctors often make treatment decisions without knowing which strand of the virus the patient is infected with.

But with Delta now accounting for a very small share of cases in most regions, the Biden administration had hoped most states would have moved away from the monoclonal antibody treatments, a senior official said.

The Biden administration has pushed for states to pivot to other treatments that have demonstrated greater effectiveness against the Omicron variant, including the Merck and Pfizer antiviral pills, GlaxoSmithKline's monoclonal antibody, AstraZeneca's pre-exposure prophylaxis, and commercially available remdesivir.

On Friday, the US Food and Drug Administration expanded the use of the antiviral remdesivir for treatment of mild to moderate Covid-19 to children and people who aren't hospitalized.