Doses of monoclonal antibodies—Covid-19 therapies authorized for emergency use last month—are sitting unused in hospital pharmacies, even as cases surge across the country.

Hospitals say the rollout of the therapies has been stunted by a lukewarm response from infectious-disease specialists, who say they want more clinical trial data before using them on a regular basis. Medical centers are also grappling with a lack of awareness and interest from both the primary-care doctors who would normally prescribe the drug and patients who are offered it. And some places are dealing with a shortage of space and staff to administer the therapies.

When monoclonal antibody therapies from Eli Lilly & Co. and Regeneron Pharmaceuticals Inc. were approved for emergency use in November, health agencies were worried there wouldn’t be enough supply to meet demand. Now, health-care providers are administering just 20% of the doses they receive each week, according to officials with Operation Warp Speed, the federal initiative to support development of new drugs, vaccines and diagnostics for Covid-19.