13 Things To Know About Paxlovid, the COVID-19 Pill

[Originally published: March 10, 2022. Updated: Dec 11, 2025]

Note: Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

Paxlovid, an FDA-approved oral antiviral pill that can be taken at home, is the go-to treatment for COVID-19. If you are at high risk for severe disease from COVID, and you take it as soon as possible within the first five days of experiencing symptoms, it will lower your risk of getting so sick that you need to be hospitalized.

Paxlovid is available to anyone ages 12 and older, depending on their risk for severe illness from COVID.

“It's really our first efficacious oral antiviral pill for this virus,” says Scott Roberts, MD, a Yale Medicine infectious diseases specialist. “It shows clear benefit, and it really can prevent hospitalization and death in people who are at high risk.”

We asked Yale Medicine infectious diseases experts common questions about Paxlovid. Below are their responses.

Paxlovid is an antiviral therapy that consists of two separate medications packaged together. When you take your three-pill dose, two of those pills will be nirmatrelvir, which inhibits a key enzyme that the COVID virus requires in order to make functional virus particles. After nirmatrelvir treatment, the COVID virus that is released from the cells is no longer able to enter uninfected cells in the body, which, in turn, stops the infection.

The other is ritonavir, a drug that was once used to treat HIV/AIDS but is now used to boost levels of antiviral medicines. As a COVID treatment, ritonavir essentially shuts down nirmatrelvir’s metabolism in the liver, so that it doesn’t move out of your body as quickly. This means it can work longer—giving it a boost to help fight the infection.

You must take Paxlovid within five days of developing symptoms.

Like all antivirals, Paxlovid works best early in the course of an illness, says Jeffrey Topal, MD, a Yale Medicine infectious diseases specialist. “Once you’ve been ill with the virus for more than a week, the damage done to the body in a severe case can’t be undone by the antiviral,” he says.

The standard dose is three Paxlovid pills twice daily (in the morning and at bedtime) for five days for a full course that adds up to 30 pills. It helps that the pills are packaged in a “dose card,” basically a medication blister pack that allows you to punch out the pills as needed. There is also a reduced dose (two pills instead of three) for people with moderate renal impairment.

“I think it's a good comparison,” says Dr. Roberts. Tamiflu is an antiviral drug that reduces flu symptoms. Both are prescription-only oral antiviral pills given early in illness.

Tamiflu is taken twice a day for five days, and it must be started within 48 hours of flu onset. “When you give a patient Tamiflu beyond that, it doesn’t really change the course of their flu,” Dr. Roberts says.

But there are also differences between the two, starting with the way they were studied, Dr. Topal adds. Researchers showed that Paxlovid can prevent hospitalization and death. But since influenza causes fewer severe cases, clinical trials focused on whether Tamiflu could shorten the length of flu illness—which it did, he says.

Paxlovid is a treatment for adults who have mild-to-moderate COVID and a condition or risk factor that increases their chances of getting severe COVID. While Paxlovid is not FDA-approved for children, it may be given to adolescents and teenagers ages 12 and older—and weighing at least 88 pounds—who have high-risk conditions under an Emergency Use Authorization (EUA). The pill is not available to younger children.

Pfizer estimates that roughly 75% of adults in the U.S. have at least one risk factor, which could include a condition such as cancer, diabetes, heart disease, pregnancy, a weakened immune system, or a mental health disorder. Adults are also at higher risk if they are unvaccinated or not up to date on their COVID vaccinations (although even if you are vaccinated, Paxlovid can provide additional protection).

You also qualify if you have certain underlying conditions or lifestyle factors that could increase the risk of progression to severe disease. These might include being age 50 or older, overweight or obese, or having a disability or a chronic disease. The Centers for Disease Control and Prevention (CDC) provides a more comprehensive list.

Some people are thought to be at higher risk because of where they live or work, or because they can’t get health care. This includes many racial and ethnic minorities, and those with disabilities, according to the CDC.

It’s important to note that although health care providers can write a prescription, pharmacists may also provide Paxlovid (with certain limitations) if they’ve opted to do so, provided you can share your electronic or printed medical records, including a list of medications you are already taking, and blood test results from the last 12 months.

Paxlovid may be given to nonhospitalized pregnant women. The American College of Obstetricians and Gynecologists states that if a pregnant patient tests positive for COVID, obstetric care professionals should prescribe Paxlovid.

But if you could become pregnant, you should know that Paxlovid may affect how hormonal contraceptives work. Pfizer recommends using an alternative form of contraception or an additional barrier method while taking Paxlovid.

Paxlovid had an 89% reduction in the risk of hospitalization and death in unvaccinated people in early clinical trials who took the drug within three days of experiencing symptoms. That figure was high enough to prompt the National Institutes of Health to prioritize it over other COVID treatments. Studies outside of the laboratory also have confirmed Paxlovid’s effectiveness among people who have been vaccinated.

In November 2022, the CDC reported on a real-world study that showed adults who took Paxlovid within five days of a COVID diagnosis had a 51% lower hospitalization rate within the next 30 days than those who were not given the drug. The study included people who had been vaccinated or had a previous infection, which the CDC said implied the drug should be offered to people who are eligible regardless of their vaccination status.

Since then, a compilation of studies has shown the greatest benefit from Paxlovid is in people who are high-risk, regardless of vaccination status or prior immunity, Dr. Roberts says.

Pfizer launched a clinical trial in March 2022 to study the safety and efficacy of Paxlovid in children and teenagers ages 6 to 17 who have COVID-19 symptoms and test positive for the virus, and who are neither hospitalized nor at risk for severe disease.

While Paxlovid is authorized for use in adolescents and teenagers ages 12 and up, and weighing at least 88 pounds, that age group wasn’t tested in the original clinical trial. But because many children reach 88 pounds—considered to be an adult weight—the FDA has allowed extensions of EUAs for medications such as monoclonal antibodies and remdesivir in younger age groups, adds Dr. Topal.

“Based on the pharmacokinetics of the drugs in Paxlovid, the differences in metabolism and excretion—liver and kidney function specifically—of these drugs in this age group are thought to be similar to that of adults,” Dr. Topal says. (Pharmacokinetics is the study of how the body interacts with administered substances for the duration of exposure.)

The most common side effects of taking Paxlovid include impaired sense of taste (for example, a metallic taste in the mouth) and diarrhea, according to the FDA. Most people who take Paxlovid should not experience serious side effects, explains Dr. Roberts. “Paxlovid is usually very well-tolerated,” he says.

But Pfizer advises people to stop taking Paxlovid and call a health care provider right away if they experience any of the following signs of an allergic reaction:

• Hives, skin rash, blisters, or peeling skin
• Painful sores or ulcers in the mouth, nose, throat, or genital area
• Trouble swallowing or breathing
• Swelling of the mouth, lips, tongue, or face
• Throat tightness
• Hoarseness of voice

Tell your healthcare professional right away if you have any of these signs and symptoms of liver problems:

• Loss of appetite
• Yellowing of your skin and the whites of your eyes (jaundice)
• Dark-colored urine
• Pale-colored stools
• Itchy skin
• Stomach-area (abdominal) pain

Since Paxlovid is cleared by the kidneys, dose adjustments may be required for patients with mild-to-moderate kidney disease, including those who have severe kidney failure and/or are undergoing dialysis, explains Dr. Roberts. Paxlovid is not recommended for those with severe liver disease; the levels of the drug can become too high and could cause increased side effects, he says.

The FDA has a fact sheet on Paxlovid with a full list of known side effects. It encourages anyone who has negative side effects from prescription drugs to visit www.fda.gov/medwatch or call 1-800-FDA-1088.

There is a long list of medications Paxlovid may interact with, and in some cases, doctors may not prescribe Paxlovid because these interactions may cause serious complications.

These medications include some organ anti-rejection drugs that transplant patients take, as well as more common drugs like some used to treat heart arrhythmias. Paxlovid decreases the metabolism of anticoagulants, or blood thinners, that many older adults depend on, driving up levels of those medications in the body to a point where they are unsafe, Dr. Topal explains.

Anyone who has Human Immunodeficiency Virus 1 (HIV-1) infection should talk to their health care provider before taking Paxlovid, since it may lead to some HIV-1 medicines not working as well in the future.

Paxlovid also interacts with common medications, including cholesterol-lowering statins like Lipitor. But in many cases, patients can talk to their doctors about taking a temporary break from some of those drugs while taking Paxlovid, Dr. Topal adds. “As always, patients should speak with their providers when starting new medications and follow their providers’ directions regarding the stopping or holding of any medications.

There have been reports of a “rebound” of COVID symptoms in some people within 2 to 8 days after completing the five-day course of Paxlovid; in those cases, some have tested positive again but have no symptoms; others have a recurrence of symptoms. Pfizer had said that in the clinical trial for Paxlovid, several participants appeared to have a rebound in virus levels, although this also occurred in some people who were given a placebo.

Some people have reported a “rebound” of COVID symptoms within days of completing their five-day course of Paxlovid. But other people who didn’t take the drug also have reported rebound symptoms in the days after testing negative for COVID.

Scientists are still studying the rebound effect. The CDC says a rebound does not mean a person was resistant to Paxlovid, nor does it mean they were reinfected with the virus. It has advised medical providers that a brief return of symptoms may be part of the natural history of SARS-CoV-2 infection in some people, independent of treatment with Paxlovid. Medical providers should advise people experiencing rebound to isolate to prevent further transmission, the agency says.

“The hypothesis is that the immune system didn’t have a chance to see the full extent of the virus, since Paxlovid suppressed replication early in disease,” Dr. Roberts says. Scientists are studying the effects of longer treatment durations, longer periods of isolation, and other ways of managing the problem, he adds.

There are other therapies for COVID, and anyone who cannot take Paxlovid—perhaps because it would interact with another medication—should talk to their doctor about the best approach for their situation.

When COVID is circulating, vaccination, testing, and mitigation efforts such as masking, remain key parts of prevention, says Dr. Topal. He encourages taking a test even if you think you only have a cold or allergies.

People also should remember that Paxlovid is not perfect, and even if it were, viruses can mutate and develop resistance to antiviral medications. “Will some people still be hospitalized? Yes—no medication is perfect,” he says. “But for many high-risk patients, this medication can really reduce that risk.”

Information provided in Yale Medicine articles is for general informational purposes only. No content in the articles should ever be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider with any questions you have regarding a medical condition.