Scientists are working on an anti-viral pill to treat COVID-19 in its earliest stages. Antivirals are already essential treatments in other diseases, such as hepatitis C and HIV, according to NBC News.

Tamiflu, a widely prescribed treatment for influenza, reduces the risk of hospitalization and the duration of illness if given in a timely manner. Scientists are hoping the new anti-viral pills to treat COVID-19 will have a similar result.

“Antivirals have the potential to not only curtail the duration of one’s COVID-19 syndrome, but also have the potential to limit transmission to people in your household if you are sick,” explained Dr. Timothy Sheahan, a virologist and assistant professor at the Gillings School of Global Health at the University of North Carolina.

Experts say there are at least three promising antivirals for COVID-19 being tested in clinical trials. They work by boosting the immune system to fight infection and blocking receptors so that viruses can’t enter healthy cells. Results from these trials should be available by fall or winter.

According to NBC, the top contender is an oral medication called molnupiravir, manufactured by Merck & Co. and Ridgeback Biotherapeutics. It causes the enzyme that helps replicate the virus to make so many errors that the pathogen can’t reproduce. This reduces the viral load and infection time and prevents a dangerous immune response that could lead to serious illness and death.

Two other oral antiviral candidates are one from Pfizer, known as PF-07321332, and AT-527, a medication developed by Roche and Atea Pharmaceuticals.

The antiviral remdesivir has been approved by the Food and Drug Administration (FDA) for the treatment of COVID-19, but it must be administered intravenously in a hospital or other healthcare setting.

The new antiviral candidates can be given in pill form.

In early trials, molnupiravir successfully reduced the levels of infectious virus quickly and Merck CEO Robert Davis said that with phase III clinical trials wrapping up shortly, the company will seek emergency use authorization (EUA) from the FDA before the end of this year. Pfizer and Atea also expect results of their clinical trials in the next few months and if emergency use is granted, we could have these treatments available soon after that for millions of people diagnosed with COVID-19.

“When we get there, that’s the idea,” said Dr. Daniel Griffin, an expert in infectious diseases at Columbia University, according to NBC. “To have this all around the country so that people can get it the same day they get diagnosed.”

Antiviral drugs are getting a lot of attention these days. The Biden administration in June agreed to buy 1.7 million doses of the Merck antiviral at a cost of $1.2 billion if the drug is approved by the FDA.

Merck said it could produce over 10 million courses of therapy by the end of 2021 if it received emergency use authorization.  Griffin noted that antiviral pills are no substitute for vaccination, adding that they would be another tool to fight COVID-19.

“It’s nice to have another option,” he said.