President Trump had taken one of the treatments, made by Regeneron, in October and promoted it as a “cure.” Early trial data had shown the treatments could keep people at risk of severe disease out of the hospital if administered soon after infection with the coronavirus.

But in a surprising turn of events, the treatments are sitting unused in hospital refrigerators around the country, just when they might do the most to help patients and relieve the burden on overwhelmed hospitals as cases and deaths surge to record levels.

The federal government has on hand nearly 532,000 doses of the two drugs, and 55 percent of that has been shipped out, according to the Department of Health and Human Services. But early data collected from hospitals by the federal government suggest that they have given only about 20 percent of their supply to patients.

Hospitals and clinics, staggered by the needs of the sick and gearing up to help administer the new coronavirus vaccines, have not focused as much attention on these treatments, which have to be infused into patients in a narrow window of time, within 10 days of when they start showing symptoms, but before they’re sick enough to be hospitalized. Administrators have struggled to identify people who should get the antibody drugs because of delays in testing and a lack of coordination between testing sites and hospitals.

And demand from patients themselves has been weaker than expected. Some have been reluctant to venture out of their homes to get the therapies in hospitals — or perceive the treatments aren’t available to them but are going to well-connected people like Chris Christie, the former Republican governor of New Jersey, and Ben Carson, the housing secretary in the Trump administration.

“There were politicians getting it, and bragging about it, or whatever, and then people thought, well it’s not for me — it’s for those people,” said Dr. Daniel M. Skovronsky, chief scientific officer of Eli Lilly, which manufactures one of the antibody treatments.

Federal and state health officials have had to take the extraordinary step of urging patients to seek out treatments that were once expected to be snatched up.

— Katie Thomas and Rebecca Robbins