The FDA Grants Emergency Use Authorization to Pfizer's COVID Pill—Here's What to Know About Paxlovid

The US Food and Drug Administration (FDA) has issued an emergency use authorization (EUA) for Pfizer's Paxlovid, the first oral antiviral for the treatment of mild-to-moderate COVID-19.

The pills can be used by adults (as well as children 12 years or older who weigh at least 88 pounds) who test positive for COVID and who are at high risk for progression to severe COVID-19 (ie, hospitalization or death), according to the FDA's December 22 announcement.

The authorization comes after data showed that Paxlovid was effective at preventing severe COVID-19 in those who take the antiviral treatment within days of symptom onset.

"Today's authorization introduces the first treatment for COVID-19 that is in the form of a pill that is taken orally—a major step forward in the fight against this global pandemic," Patrizia Cavazzoni, MD, director of the FDA's Center for Drug Evaluation and Research, said in the FDA announcement. "This authorization provides a new tool to combat COVID-19 at a crucial time in the pandemic as new variants emerge and promises to make antiviral treatment more accessible to patients who are at high risk for progression to severe COVID-19."

The data, which was initially released by Pfizer on December 14, found that, when compared to a placebo, there was an 89% reduced risk of hospitalization or death when people with a mild to moderate COVID infection who were at high risk for developing a severe infection took Paxlovid within three days of symptom onset. There was an 88% lower risk of hospitalization or death when the pill was taken within five days of symptom onset.

Experts agree that Paxlovid could be a big deal in the fight against COVID-19. But with the treatment option being so new, it's more than understandable that you might have questions about how the pill works and what, exactly, it means for you. Here's what to know.

What is Paxlovid, exactly?

A COVID pill is an antiviral medication that can help lower the risk of severe COVID-19 in people who catch the virus, Thomas Russo, MD, professor and chief of infectious disease at the University of Buffalo in New York, tells Health. Pfizer's pills are a combination of nirmatrelvir, a new antiviral medication, and ritonavir, an antiretroviral medication that's currently used to treat HIV/AIDS.

Dr. Russo compares Paxlovid to Tamiflu, an antiviral medication that's designed to help lower the risk of severe illness in people who contract the flu. However, it stands to be even better, says infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore. "This is not just a Tamiflu equivalent," tells Health. "It is much better than Tamiflu is for influenza."

How does Paxlovid work?

You'll need a prescription for Paxlovid. Once you have that, you should start the treatment as soon as possible after diagnosis of COVID-19 and within five days of symptom onset, according to the FDA authorization announcement.

Paxlovid is administered as three tablets (two tablets of nirmatrelvir and one tablet of ritonavir) taken together orally twice daily for five consecutive days. That means that, in all, you'd be taking 30 tablets.

As for how the treatment actually works, that happens in two ways. The nirmatrelvir blocks the activity of SARS-CoV-2-3CL protease, a particular enzyme the virus needs in order to replicate, Pfizer explains. When the virus can't replicate, it can't make you sick, Dr. Russo says. Meanwhile, a low dose of ritonavir helps slow the breakdown of nirmatrelvir in the body to allow it to remain active for longer periods of time at higher concentrations to fight the virus.

As a whole, the medication "interferes with the virus multiplying and its ability to make you sick," says William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine in Nashville.

How effective is Paxlovid?

Laboratory results are promising. The study that was used as a basis for the authorization focused on 2,246 unvaccinated people who are at high risk for developing severe complications from the virus. And again, among this population, the study found that the COVID pill was 88% to 89% effective at preventing hospitalization or death.

Laboratory findings also suggest that Paxlovid might prevent a COVID infection of the Omicron variant from developing into a severe infection.

Pfizer is also studying the pill in people who are at "standard risk" of complications and have so far found that there was a 70% reduced risk in hospitalization and no deaths among this study population.

"These are impressive findings and will be a welcome addition to the toolbox we have for COVID treatment," Dr. Adalja says. The only caveat, according to Dr. Schaffner, is that the COVID pill will likely be less effective when it's used in the real world. "Real world results are always less impressive than lab studies," he says.

Pfizer CEO Albert Bourla estimates that 1,200 deaths and 6,000 hospitalizations will be prevented for every 100,000 COVID-19 patients who take the pills, according to reporting from ABC.

As with any medicine, the treatment does come with possible side effects, including impaired sense of taste, diarrhea, high blood pressure, and muscle aches, per the FDA.

Who can use Paxlovid?

As of right now, Pfizer's pills received authorization for use in people who are at a high risk of developing severe forms of COVID-19. That means, if and when it's authorized or approved for use, it's unlikely that you'll be able to get it unless you have certain risk factors for severe COVID, like obesity, certain lung conditions, or diabetes.

You'll also need a prescription for it, which means acting quickly at the first sign of symptom is key to getting the proper care you need. "People tend to be in denial early on," Dr. Russo says. "By the time they talk to their doctor, get tested, get the results, and get their prescription filled, it could be close to that five-day window." Also, not everyone has a doctor, he points out, which can make the process tricky, since getting the medication sooner rather than later is best. "The earlier you give an antiviral, the better it works," Dr. Russo says.

And as the agency points out, "Paxlovid is not authorized for the pre-exposure or post-exposure prevention of COVID-19 or for initiation of treatment in those requiring hospitalization due to severe or critical COVID-19."

Can Paxlovid replace the COVID vaccine?

That's a hard no from doctors. "Prevention through vaccination is always better than treatment," Dr. Adalja says. "But it is awesome that there will be an effective oral antiviral available."

Dr. Schaffner agrees. "This is no substitute for vaccination," he says. "You don't want to get infected if you don't have to, and this is not 100%, even if it works very rapidly and everything is done exactly as planned as was done in these research studies."

Are there other COVID pills in the works?

Merck also has a COVID pill, called molnupiravir, which has had less impressive data than Pfizer's COVID pill. Early data showed that the pill cut hospitalizations and deaths by 50%, but later data suggested it was actually only 30% effective. There are also concerns that the Merck pill could pose risks to pregnant people and harm their developing fetus. Merck has submitted its data to the FDA, but the process seems to have stalled.

But for now, there is the Pfizer COVID pill, and the company says that the delivery of 10 million treatment courses that it had promised the US government should be completed in 2022.