New oral antiviral medications that can prevent severe COVID-19 show promise for slowing hospitalizations and deaths. But with the drugs in short supply and many hospitals and pharmacies still waiting for their first deliveries, not everyone who is eligible for the medication can get it.

Late last year, the U.S. Food and Drug Administration gave emergency use authorization to Pfizer’s Paxlovid and Merck’s molnupiravir, both of which treat COVID-19 and have been effective in preventing severe illness if taken shortly after symptoms start. The drugs aren’t intended for everyone who gets sick — only for people who are at high risk of developing severe illness and who meet criteria set by the FDA are eligible for a prescription.

Until the pace for deliveries picks up, being eligible for the drug doesn’t mean you’ll be able to get it.

“We wanted to ensure everyone who really needs this medication has a fair shot at getting it,” said Sarah Schenck, the medical director of virtualist medicine at ChristianaCare’s Center for Virtual Health. At the same time, she said, “we do need to make decisions. There is that certain aspect of triaging who has the greater risk of severe disease.”

Not only are supplies scarce, at Philadelphia-area pharmacies and hospitals, these drugs aren’t cheap. Under bulk purchase agreements, the federal government is paying about $530 for a course of Paxlovid and $700 for a course of molnupiravir. The government’s deals with Pfizer and Merck will make the drugs available to millions of people for free, though coverage could change in the future.

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Both Paxlovid and molnupiravir are primarily intended for patients who have not been hospitalized, though the drugs can be used in hospitals, too.

Studies have shown that people who were at high risk of severe illness benefited the most from the medications. But one limitation of early studies is that they were conducted among unvaccinated people. Schenck said doctors believe the medications will also be helpful for vaccinated people who are at an elevated risk because of age and underlying conditions, though for most people vaccination means they won’t need antivirals.

Under the FDA’s emergency use authorization, the medications can be prescribed only to people who are considered “high risk,” such as older adults, people with compromised immune systems, or those with conditions such as diabetes or obesity, or who smoke.

ChristianaCare received a small shipment of the antiviral medications earlier in January and is establishing a system for determining which patients should receive a prescription. In other words, they have to determine who among their high-risk patients is most vulnerable and so would benefit most from the medication.

Using data from the thousands of COVID-19 patients the health system has treated since the beginning of the pandemic, ChristianaCare will develop an algorithm to help predict who is most likely to suffer the virus’ worst effects.

The health system uses a similar approach to determine which COVID-19 patients should get monoclonal antibody treatments, administered by injection or infusion. These, too, are costly, both because of medication itself and the labor required to administer it.

Last year, the federal government agreed to pay $2,100 per treatment for infusion medications by GlaxoSmithKline and Vir Biotechnology, and Regeneron, which means patients do not pay for the medication. Medicare agreed to cover fees charged by hospitals and infusion centers to administer the drug, but coverage may vary for people with private insurance.

Other Philadelphia-area health systems, including Penn Medicine and Virtua Health, are still waiting for their first deliveries of the new antiviral pills.

PJ Brennan, Penn Medicine’s chief medical officer, said in a statement that he hopes the health system will receive the medications “in the coming weeks.” In the meantime, Penn is working with pharmacies to get the medication to patients who are eligible, he said.

Just 28 pharmacies — mostly Rite Aid or Walgreens stores — in Philadelphia and the surrounding counties have one or both of the antiviral medications, according to a database maintained by the U.S. Department of Health and Human Services.

Pharmacist David Stone owns Professional Pharmacy of Pennsburg, one of six Montgomery County pharmacies that received the medications earlier in the month. Health care providers aren’t flooding the market with prescriptions, he said.

“We’re getting a lot of phone calls, but not a ton of scripts,” he said. The pharmacy has filled a dozen prescriptions for Paxlovid and none of molnupiravir.

In addition to patients wanting to know how they can get the medication, the pharmacy has heard from several hospitals that are trying to identify where to refer their patients to fill a prescription.

Stone said he thinks supply will begin to flow more smoothly over the next few weeks.

In the meantime, Schenck urged people to get vaccinated.

“The largest and most powerful tool in our toolbox is still vaccination,” she said. “The best way to treat this disease is to prevent this disease.”