The US Food and Drug Administration (FDA) approved for emergency use Pfizer’s Paxlovid, the first oral pill meant to treat mild-to-moderate COVID-19 infection in patients who are at high risk of progressing to severe illness.

“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,” said Patrizia Cavazzoni, MD, director of the FDA’s Center for Drug Evaluation and Research, in a press release.

The pill is authorized for patients ages 12 and older, and should be started within 5 days of COVID-19 symptom onset. It could be available for US doctors to prescribe in a matter of days.

Paxlovid is a combination of Pfizer’s investigational antiviral PF-07321332 and a low dose of ritonavir, an antiretroviral medication traditionally used to treat H.I.V. “The treatment disrupts the replication of SARS-CoV-2 in the body by binding to the 3CL-like protease, an enzyme crucial to the virus’ function and reproduction.”

An interim analysis showed that the drug was 85 percent effective when taken within five days of the start of symptoms. This could potentially be more effective than Pfizer’s main competition for the pill, made by Merck and Ridgeback Biotherapeutics, called molnupiravir, which reduces the risk of hospitalization and death from Covid-19 by 30 percent if taken within five days of the onset of symptoms.

In addition to being potentially more effective, Paxlovid may encounter fewer safety questions than Merck’s pill. Some experts have expressed concerns that “molnupiravir’s mechanism of action against Covid-19 – mimicking R.N.A. molecules to induce viral mutations– could also introduce harmful mutations within human D.N.A.” Paxlovid, a different type of antiviral known as a protease inhibitor, has shown no signs of “mutagenic D.N.A. interactions,” Pfizer has said.

The White House confirmed recently that the federal government had ordered enough Paxlovid to treat 10 million Americans. The U.S. will have more than “250,000 courses of treatment available in January,” says President Biden. “As Pfizer works to produce these treatments as quickly as possible, we will work closely with them and provide any resource needed, including using the Defense Production Act if warranted.”

The U.S. government has agreed to pay $5.29 billion to purchase 10 million treatment courses that Pfizer will deliver by the end of next year. The drug will be free to patients who are prescribed to by a medical professional.

Some researchers have raised safety concerns, because Paxlovid is taken with another drug. The second drug, called ritonavir, helps Paxlovid fight the virus longer, but can cause side effects when taken with certain widely used heart and cholesterol medicines.

Under the authorization, the FDA said Paxlovid shouldn’t be used with certain drugs for conditions including cancer, irregular heart rhythms and depression.

Accordinf to the Wall Street Journal, “The FDA also recommended against giving Paxlovid to patients with severe kidney disease or liver impairment and said patients with moderate kidney issues should take a reduced dose. In patients with moderate renal impairment, a reduced Paxlovid dose is needed, it said.”

The pill’s key advantage over most existing treatments is that patients can easily take them at home, unlike antibody therapies or the antiviral Veklury that usually require administration at a clinic or hospital.

“This breakthrough therapy, which has been shown to significantly reduce hospitalizations and deaths and can be taken at home, will change the way we treat Covid-19,” said Pfizer Chief Executive Albert Bourla.

When asked for her opinions on a COVID-19 Pill being released, Junior Daphne Saatcioglu said “I have no idea how effective the treatment is, but I’m hoping the cases start to stop rising soon. I got Covid this month and I can say that I definitely did not miss being home all day. Hopefully, like the vaccines, the pill is another step towards normal.”