Multiple factors have conspired to put a damper on use of oral COVID-19 antiviral treatment Paxlovid, according to a report published Tuesday.

Complicated eligibility requirements and reduced testing, as well as the perception that Omicron infections are relatively mild, are among the reasons why Paxlovid supply has well outpaced demand in countries like the United States, Japan and South Korea. 

In the fall, interim trial data showed Paxlovid winning an efficacy showdown, 89% to 50%, against Merck’s oral antiviral molnupiravir in the high-risk setting. That, along with a superior side-effect profile, impressed infectious disease experts sufficiently to declare Paxlovid the better drug. It’s also more convenient to take than Gilead’s remdesivir, which is administered intravenously.

The drugmaker had plans to produce up to 120 million courses of Paxlovid this year and expects at least $22 billion in sales from contracts signed through early February. But even with COVID-19 infections again on the rise, utilization of Pfizer’s pill is far off forecast, the report noted, citing data from health ministries and interviews with HCPs.

In the weeks following emergency authorization of the Merck and Pfizer pills, prescribers had trouble tracking them down. These days, though, supply isn’t an issue. 

Take the U.S. market. Through the first half of April, the U.S. has distributed around 1.5 million courses and pharmacies still have over 500,000 available. That’s out of more than 3.5 million courses earmarked by month’s end. 

Uptake is another matter. The pharmacy director at one health system in Utah, where cases are low, said that its four large health centers had dispensed just two Paxlovid courses on one day in April. That’s despite having about 80 courses on hand at each center.

In addition to lower COVID-19 case counts leading to lower overall utilization of COVID-19 therapeutics, safety was another factor cited. One of Paxlovid’s key ingredients, ritonavir, is notorious for having drug/drug interactions

Some U.S. pharmacists and doctors also warned that, because more patients are opting for home tests over laboratory testing, those at high risk might be unaware they’re eligible for Paxlovid — or that it even exists.

The situation overseas isn’t much better. In Asia, which has seen record infection rates, the rollout has been sluggish. Japan, whose health ministry restricts which facilities can prescribe the pill, has doled out 2,900 courses out of 10,000 sent. South Korea has utilized a mere third of its inventory.

Access restrictions have also hampered the drug’s European debut, said Pfizer CEO Albert Bourla. According to England’s National Health Service, the pill has been given to about 6,000 patients; the country contracted to receive 2.75 million courses. In Italy, 8,300 people have been prescribed the pills. 

Demand could pick up if the drug is shown to work in broader treatment groups. Studies are underway testing Paxlovid in low-risk patients and the vaccinated, the report noted.