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Health officials are renewing their pleas to eligible Americans to get prescriptions to Paxlovid, Pfizer’s COVID pills, to curb their risk of hospitalization and death from the disease, as COVID-19 cases and hospitalizations rise. President Biden announced Thursday that he has contracted COVID and that he is taking Paxlovid to treat its symptoms 

Figures published by the Biden administration this week count more than 2.7 million twice daily, five day courses of Paxlovid, or “ritonavir-boosted nirmatrelvir,” that have been taken by patients through July 17. The drugs themselves are purchased and distributed for free by the federal government.

Use of Paxlovid far outstrips that of  other available COVID-19 treatments authorized by the Food and Drug Administration, like Merck’s Lagevrio antiviral pills or the monoclonal antibody drug bebetelovimab from Eli Lilly. 

Here’s the latest about what we know about the pills: 

Who’s eligible to take Paxlovid pills?

In December, the FDA authorized use of Paxlovid to treat COVID-19 in adults, as well as children who weigh at least 40 kilograms, or around 88 pounds.

The agency’s checklist for prescribing Paxlovid also requires that patients: 

  • Test positive for the virus, including by either by a lab swab or at-home rapid test
  • Have at least one risk factor” for severe COVID-19, like being older than 65 years old or underlying conditions like asthma
  • Show COVID-19 symptoms, that started less within five days ago, which aren’t so severe to require hospitalization 

There are some additional reasons that can disqualify people from being able to take Paxlovid, like having severe kidney failure (also known as “renal impairment”).

Several commonly used drugs, like the cholesterol drug rosuvastatin or the seasonal allergy spray fluticasone, also risk potentially dangerous interactions with ritonavir, a key component of Paxlovid. 

Each dose of Paxlovid is made up of three total tablets that patients must swallow: two of nirmatrelvir and one of ritonavir, which is needed to boost its effectiveness. 

In these cases, doctors can help their patients figure out whether to cut back or pause the use of their other medications while taking Paxlovid. 

“Potential drug interactions are an important consideration. However, several commonly used medications with potential interactions such as statins, oral contraceptives, and HIV medications can be easily managed under provider supervision,” the FDA’s top drug official, Dr. John Farley, recently said on a podcast posted by the agency.

Where can I get a prescription for Paxlovid

Pfizer’s pills have been distributed around the country to thousands of pharmacies and health systems around the country. 

To get a prescription for the drug, health officials have been advising Americans to turn first to their primary care or family physician. 

However, health authorities have also deployed other ways to try to make it easier to obtain the pills. 

For example, the Biden administration has been touting “test to treat” sites where Americans can get tested for the virus, get a prescription from a healthcare provider, and then fill their prescription all at one location. 

These include places like health centers or health clinics based at the same location as a drug store.

Last month, the FDA also said it would allow pharmacists to prescribe and dole out Pfizer’s Paxlovid pills on the spot under some limitations

However, many pharmacies say it will take a while for them to sort out policies and reimbursement with insurers before rolling out the process. The Centers for Medicare and Medicaid Services also says that Medicare cannot cover the cost of pharmacists prescribing the drug, under law.

“Pharmacist prescribing of Paxlovid will take time to implement and operationalize,” the National Association of Chain Drug Stores wrote in a letter to the Biden administration last week.

How effective is Paxlovid and what do we know about rebound infection?

The FDA’s initial authorization of Paxlovid was based on a trial run by Pfizer in at-risk unvaccinated adults. Its results showed that patients’ risk of severe COVID-19 was 89% lower, compared to a placebo. 

Lab data published this week in The New England Journal of Medicine also suggest that Paxlovid works against the BA.5 subvariant now dominant in the U.S.

However, the company has also disclosed that other trials it has since run among “standard-risk” patients – which included people with at least one risk factor who were also vaccinated – fell short of their goals, though they showed some improvement. 

Other studies have also turned up more modest improvements in real-world use of Paxlovid. 

In a study through February that has yet to be peer-reviewed, doctors at Massachusetts General Brigham found that the drug appeared to lower the risk of Omicron hospitalization by 45% among patients who were prescribed Paxlovid. A healthcare system in Israel turned up a similar 46% risk reduction.

That has led to concerns among some doctors that doctors may be overprescribing Pfizer’s pills, which could raise the risk that  the virus may eventually develop resistance to the drug. 

These concerns have been compounded by reports of so-called “rebound” cases, where patients appear to fully recover after completing Pfizer’s pills only to see symptoms later return for a few more days. 

“After I finished the five days of Paxlovid, I reverted to negative on an antigen test for three days in a row. And then on the fourth day, just to be absolutely certain, I tested myself again. I reverted back to positive,” Dr. Anthony Fauci, the president’s chief medical adviser, told Foreign Policy last month.

Nonetheless, Fauci said he ended up taking a second course of Paxlovid to battle his rebound symptoms.

Scientists are already trying to study how often and why these rebound cases occur. 

A review of Pfizer’s original trial data published by the FDA found that a rebound in virus shed by patients, under the broadest definition, may have happened in as many as 8.1% of trial participants who took Paxlovid compared to 5.4% of those who got a placebo. 

The agency also asked Pfizer to study how these “viral RNA rebounds” are translating into an actual return of symptoms, though it acknowledged that accurately investigating this “likely will be challenging due to a lack of objective, standardized measures for identifying and quantifying mild COVID-19 symptoms.”