Publisher Health

The Food and Drug Administration on Wednesday authorized the first pill for Covid-19, offering a highly effective defense against severe illness that will arrive as the country endures another major surge of the pandemic.

The drug, developed by Pfizer and known as Paxlovid, is authorized for Covid patients age 12 and over who are vulnerable to becoming severely ill because they are older or have medical conditions such as obesity or diabetes. Tens of millions of Americans — including both vaccinated and unvaccinated people — will be eligible if they get infected with the virus. The treatment could be available within a few days.

Pfizer’s laboratory studies indicate that its pills are likely to work against the Omicron variant, which has rapidly become the dominant form of new cases in the United States.

A clinical trial indicated that Paxlovid is highly effective when taken soon after people start feeling sick. In a final analysis of a key study conducted while the Delta variant was surging, Pfizer’s drug reduced the risk of hospitalization or death by 88 percent when given to high-risk unvaccinated adults within five days of the start of their symptoms.

Paxlovid appears to be substantially more effective than a similar antiviral pill from Merck, known as molnupiravir, that is still awaiting authorization by the F.D.A. In a clinical trial, Merck’s drug reduced risk of hospitalization and death for high-risk patients by 30 percent.

Until now, monoclonal antibody drugs, which are typically infused into the bloodstream at a hospital or clinic, have been the only authorized treatments for Covid patients who are not hospitalized but at higher risk of developing severe disease. But the antibodies have gone to fewer people than the pills are expected to reach, and most of the country’s supply of the antibody treatments is unlikely to work against Omicron.

The federal government has ordered enough of Pfizer’s pills to cover 10 million people, at a cost of about $530 per patient, but the supply will be limited at first.

Within a week, Pfizer is expected to make available to the United States enough of its pills to cover 65,000 Americans. At current infection rates, that would be enough supply for less than one day if it were given to half of people in the United States who test positive for the virus.

Pfizer is expected to make available to the United States another 200,000 treatment courses in January. The pace of deliveries is expected to increase sharply in the subsequent months, with Pfizer expected to fulfill the government’s full order by late summer.

Coronavirus cases have been increasing since early November, particularly in the Midwest and Northeast, driven first by the Delta variant and now mostly by Omicron.

The federal government will allocate the antiviral pills to states, which can then distribute them to local health departments and pharmacies, as was done with Covid vaccines. The government will also distribute the pills directly to community health centers.

“The tough thing for states to figure out is who to make it available to, since there’s so few to begin with,” said Dr. Nahid Bhadelia, director of the Center for Emerging Infectious Diseases Policy and Research at Boston University. “You want to make sure that it’s at least given to people who are the most likely to benefit from it.”

She said it would be important for state and local governments to prioritize getting the pills to medically vulnerable people, particularly in nursing homes and clinics in hard-hit communities.

To get Pfizer’s pills, the F.D.A. said, patients will need to test positive for the virus and get a prescription from a health care provider, all within no more than five days after their symptoms start. Those requirements may pose serious challenges.

While the agency did not specify which type of test will be needed, over-the-counter rapid antigen tests, which return results within 15 minutes, are expected to be widely used. President Biden announced on Tuesday that the administration is buying 500 million rapid tests to distribute free to the public, but it is not clear if that will be enough to meet what is expected to be very high demand.

There is also a risk that Americans most in need of the pills will refuse them, just as they have spurned vaccines. About half of unvaccinated adults polled by Morning Consult said they would not take F.D.A.-authorized antiviral pills if they got sick with Covid.

Pfizer expects to produce 120 million courses of Paxlovid in 2022. The company already has deals to sell its pills to a number of wealthy countries, and says it’s in discussions with dozens of governments around the world about additional supply deals. It has also agreed to allow other manufacturers to inexpensively make and sell the pills to poorer countries.

The European Medicines Agency last week recommended Paxlovid to treat adults with Covid who are at risk of severe disease, paving the way for European nations to begin using it soon.

Pfizer’s treatment is meant to be taken as 30 pills over five days. Patients take three pills at a time: two of Pfizer’s pills and one of a low-dose H.I.V. drug known as ritonavir, which helps Pfizer’s drug remain active in the body longer.

The F.D.A. said that Paxlovid should not be taken with certain medications, including a commonly used statin, because ritonavir can interfere with them, potentially causing serious side effects. With certain drugs, health care providers may need to recommend that patients stop taking their usual medication for a few days or adjust its dosage.

Pfizer, already flush with cash from its record-setting Covid vaccine, stands to get another windfall from its new pill, which originated in a company laboratory during the SARS epidemic nearly two decades ago.

Pfizer executives told analysts last week that Paxlovid could reach up to 155 million people in wealthier countries and up to 95 million people in poorer countries in 2022. They said they expected the market to be long-lasting, as governments and commercial buyers may be interested in stockpiling the pills in the coming years.

Analysts at the investment bank SVB Leerink estimated that Paxlovid would bring in $24 billion in global revenue in 2022 and $33 billion in 2023.

Merck’s treatment is also expected to win authorization this week. Within weeks, some patients may be able to choose between Pfizer’s treatment and Merck’s. Pfizer’s option, in addition to working better in staving off severe Covid, may be safer.

Merck’s pill inserts errors into the virus’s genes to stop it from replicating. While Merck has said that its studies have found that its treatment is safe, some scientists have raised concerns that could result in dangerous unintended consequences.

Paxlovid does not introduce mutations, so it has not raised the same concerns as molnupiravir. But for the first few months, Merck’s treatment is expected to be in much more abundant supply. Merck is expected to make available to the federal government enough pills for 3.1 million Americans by the end of January. The first 378,000 treatment courses are expected about two weeks after authorization.

“Clearly if people have a choice, they’re going to choose the Pfizer product,” said Dr. Walid Gellad, who directs the Center for Pharmaceutical Policy and Prescribing at the University of Pittsburgh. “There’s no doubt that the data supports better efficacy and fewer concerns about safety. The question is, how easily obtainable is the Pfizer product going to be?”