By Michael Erman

(Reuters) – The U.S. National Institutes of Health are in negotiations with Pfizer Inc (NYSE:). Dr. Anthony Fauci, top U.S. expert in infectious diseases said Wednesday that the company is interested in determining whether it would be necessary to prolong its COVID-19 antiviral treatment Paxlovid.

Fauci stated that “We are going to plan what studies we will be doing fairly soon, within the next couple of days”, in order to decide if a longer course or not during a White House COVID-19 briefing.

Rising cases of COVID-19 in the United States have prompted an increase in therapeutic use. In the United States, more than 660,000 Paxlovid prescriptions were administered so far.

Some COVID patients reported that their symptoms returned after the treatment. While some have seen improvement in their condition, it is not clear how many people have had this rebound.

Pfizer found that around 2.2% of the recipients of the two-drug treatment experienced an increase in virus load following completion of the standard course. This compares with 1.5% for placebo recipients.

Dr. Ashish Jha (White House COVID-19) stated that Delta was once the predominant variant of coronavirus. However, it’s not known if reinfections occur more frequently with Omicron.

Jha stated that Paxlovid does not appear to be hampered by reinfections in its ability to decrease COVID-19-related deaths and hospitalizations.

Pfizer suggests that Paxlovid can be used to treat reinfections with another five-day course. According to the U.S. Food and Drug Administration, there’s no current evidence that supports a second course of Paxlovid or a 10 day course.