On Monday, one of my patients called me to say she had tested positive for the coronavirus. The patient, who has sickle cell anemia and has had a bone-marrow transplant, lives several hours away from the hospital where I work in New York City. Because she is at extreme risk for complications from Covid-19, I began trying to secure the best medicine for preventing severe disease: monoclonal antibodies.

Monoclonal antibodies are made in the laboratory and are designed to mimic the immune system’s ability to fight off invaders like viruses. Different monoclonal antibodies are used to treat numerous illnesses. They have been found effective in treating people at a high risk of complications from Covid-19, and last fall the Food and Drug Administration approved their emergency use to treat the disease. But right now it’s too hard for patients to obtain this treatment.

After calls to several hospitals near my patient’s home, I found one that could administer monoclonal antibodies. She went to the hospital and remained in the emergency room for more than 24 hours, untreated because the doctors did not feel her condition warranted the medication. While she waited, she developed a sickle cell pain crisis that was doubtlessly provoked by her panic over the test result and the uncertainty about whether she would receive the treatment I recommended. By Tuesday night, she had a fever and a cough, and her treatment finally began.

As a clinical hematologist caring for people with compromised immune systems, I have watched in horror as Covid-19 has ravaged my patients. I have lost three colleagues and more than 20 patients to the disease. I contracted Covid-19 last March, before any useful treatment had been identified. Despite progress in vaccinations, the coronavirus remains a persistent and even growing problem in New York City, where about 4,000 new cases of Covid-19 are being identified every day and thousands of people remain hospitalized.

When President Donald Trump fell sick with Covid-19 in October, he received monoclonal antibodies, as did several senior members of his inner circle. All of them survived, as do nearly 90 percent of high-risk patients who are treated early with this medication.

But despite the extraordinary efficacy of monoclonal antibodies, this lifesaving treatment is often difficult for regular people to obtain. When I tried to secure insurance approval for monoclonal antibody treatment for another patient, I was told that the person, who was also at high risk for Covid-19 complications, wasn’t sick enough to warrant treatment, even though some people in danger of severe outcomes from Covid are given monoclonal antibodies before symptoms appear.

In the past month, I have given monoclonal antibodies to three high-risk patients in which Covid-19 was newly diagnosed. Two have cancer and are in their 80s, and the other is a 55-year-old who had recently received a bone-marrow transplant to treat lymphoma. Two of the patients had mild symptoms. The other felt unwell but had no symptoms of Covid.

All three patients responded well to the treatment, but each instance required me to obtain approval from the hospital’s infectious-disease, pulmonary-medicine, pharmacy and emergency departments, something I don’t typically have to do as a senior attending physician. Each time I stayed with the patient until late in the evening to ensure that the planned treatment was accomplished. Because monoclonal antibody treatment can be administered only in an outpatient setting such as an infusion center or an emergency room, in one case I had to persuade the admitting team to discharge a patient from the hospital so that they could send him to the emergency room to receive the care he needed.

A colleague and I recently called every hospital in New York City’s five boroughs to find out whether they offer monoclonal antibodies to high-risk patients with Covid-19. Only three said they could provide the therapy to a high-risk patient without symptoms. Some said they would need to evaluate a patient in their emergency room, and others either didn’t know about monoclonal antibodies or would not discuss a referral.

The federal government has delivered more than 750,000 courses of monoclonal antibody treatment throughout the country, and Medicare has waived co-payments for patients receiving it. But insurance companies reimburse hospitals only for the cost of administering the drugs. That process is time-consuming, because the medicine is infused over several hours; and because these patients have active Covid-19 infections, they must be isolated. All of this makes the delivery of monoclonal antibodies a logistical challenge and expensive for the provider.

The Biden administration has pledged to make monoclonal antibody treatment more available, with a $150 million plan to deliver it to more patients who need it. This is a welcome development, but so far, in the field, we have seen no tangible change in access to treatment.

Coronavirus vaccines are preventing infections and serious illness. For those already infected with the virus and at risk for hospitalization or death, doctors can now intervene to improve their chances of survival. The Trump administration reassured the medical community that a ventilator would be available for every patient who needs one, but many Covid-19 patients who are placed on a ventilator die. Now doctors have a better option. Hospitals and insurance companies should commit to making this effective treatment available to anyone whose life it can save. Vaccination may not be effective in patients with compromised immune systems, but monoclonal antibodies work.