Pfizer asked US regulators on Tuesday to approve its COVID-19 experimental pill, laying the foundation for a promising treatment that can be taken at home this winter.

When the company submitted its application, the number of new infections in the United States rose again, mainly due to the colder weather in hotspots in states where more Americans stay indoors.

Pfizer’s pills have been proven to significantly reduce the hospitalization rate and mortality of people infected with the coronavirus. The US Food and Drug Administration is already reviewing competing pills from Merck, and it is expected that several smaller drugmakers will also seek authorization for their antiviral pills in the next few months.

Pfizer CEO Albert Bourla said in a statement: “We are taking action as soon as possible to work hard to put this potential treatment in the hands of patients, and we look forward to working with the US FDA to review us Application.”

Specifically, Pfizer hopes that the drug can be used in adults who have mild to moderate COVID-19 infection and are at risk of serious illness. This is similar to the current way other drugs are used to treat this disease. But all FDA-authorized treatments for COVID-19 require intravenous injections or injections by health professionals in hospitals or clinics.

The FDA will hold a public meeting on Merck Pills later this month to solicit the opinions of outside experts before making a decision. The agency does not need to hold such meetings, and it is not clear whether Pfizer’s drugs will undergo similar public review.

Some experts predict that COVID-19 treatment will eventually be combined to better prevent the worst effects of the virus.

Pfizer reported earlier this month that its pills have reduced the number of hospitalizations and deaths of high-risk adults with early symptoms of COVID-19 by 89%. The company studied its pills in people who have not been vaccinated and are at greatest risk of the virus due to health issues such as age or obesity. If authorized, the FDA will have to weigh whether to provide such pills to vaccinated people who treat breakthrough infections because they are not part of the initial testing.

For best results, patients need to start taking the medication within three days of the onset of symptoms, which emphasizes the need for rapid testing and diagnosis. If another COVID-19 surge caused the delays and shortages in testing that occurred last winter, this could be a challenge.

Pfizer’s drug is part of a decades-old family of protease inhibitor antiviral drugs, which revolutionized the treatment of HIV and hepatitis C. These drugs block a key enzyme required for the virus to multiply in the human body. This is different from Merck pills, which cause tiny mutations in the coronavirus until it is unable to replicate itself.

On Tuesday, Pfizer signed an agreement with a United Nations-backed organization that allows generic drug manufacturers to produce low-cost versions of pills for certain countries. There is a similar deal for Merck’s pill, which was licensed in the UK earlier this month.

The United States has approved another antiviral drug for COVID-19, Remdesivir, and approved three antibody therapies that help the immune system fight the virus. But they usually have to be administered by health professionals through time-consuming infusions, and the limited supply is strained by the last surge in delta variants.

The US government has pledged to buy Merck’s pills. According to an official familiar with the matter, federal authorities are negotiating with Pfizer to purchase millions of pills.