(CNN) The US Food and Drug Administration on Thursday authorized Merck's antiviral pill, molnupiravir, to treat Covid-19 "for the treatment of mild-to-moderate coronavirus disease (COVID-19) in adults with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death, and for whom alternative COVID-19 treatment options authorized by the FDA are not accessible or clinically appropriate."
This is the second Covid-19 antiviral pill authorized for ill people to take at home, before they get sick enough to be hospitalized. Merck has an agreement with the US government for the company to supply 3.1 million courses of molnupiravir upon this authorization.
Molnupiravir was narrowly recommended by the FDA's advisers in a 13-10 vote at the end of November after data showed it cut the risk of hospitalization or death by 30% among high-risk adults. This was lower than an earlier analysis suggesting that number could be about 50%.
Dr. Eliav Barr, senior vice president of global medical affairs at Merck, told CNN this month that he was optimistic this treatment would work against the Omicron variant.
"The Omicron variant is primarily different from the other types of Covid at the spike protein. Our drug works in completely different part of the virus. So we're very optimistic that the drug will continue to be effective against Omicron, and we're studying that right now."
On Wednesday, the FDA authorized Pfizer's antiviral pill, Paxlovid, to treat Covid-19, the first antiviral Covid-19 pill authorized in the US for ill people to take at home, before they get sick enough to be hospitalized. High-risk individuals age 12 and older who weigh at least 88 pounds and have a positive SARS-CoV-2 test are eligible for this treatment and will need to have it prescribed by a doctor.
The pill "should be initiated as soon as possible after diagnosis of Covid-19 and within five days of symptom onset," according to an FDA statement.
Paxlovid combines a new antiviral drug named nirmatrelvir and an older one called ritonavir and is administered as three pills given twice a day for five days.
Last week, Pfizer released updated results that showed the treatment cut the risk of hospitalization or death by 89% if given to high-risk adults within a few days of their first symptoms. If given within the first five days of symptoms, the efficacy was similar: 88%.
"Today's authorization of PAXLOVID represents another tremendous example of how science will help us ultimately defeat this pandemic, which, even two years in, continues to disrupt and devastate lives across the world. 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, and hopefully help reduce some of the significant pressures facing our healthcare and hospital systems," Pfizer Chairman and CEO Albert Bourla said in a statement. "Pfizer stands ready to begin delivery in the U.S. immediately to help get PAXLOVID into the hands of appropriate patients as quickly as possible."
In November, the Biden administration announced that it would purchase 10 million treatment courses for $5.295 billion. President Biden said he was encouraged by the "promising data" from Pfizer and said the drug would "mark a significant step forward in our path out of the pandemic."
He called Paxlovid a "potentially powerful tool in our fight against the virus, including the Omicron variant," but stressed that getting vaccinated and receiving a booster shot remained "the most important tools we have to save lives."
The FDA emphasized in a statement that Paxlovid is not for pre- or post-exposure prevention of Covid-19 and "is not a substitute for vaccination in individuals for whom COVID-19 vaccination and a booster dose are recommended."
Remdesivir, sold under the brand name Veklury, is the only antiviral approved by FDA for treatment of Covid-19. It's given intravenously, not as a pill that can be taken at home.