UPDATE 3-FDA advisers back Pfizer's COVID treatment for full approval

(Adds FDA decision time frame, meeting details, background)

By Leroy Leo and Khushi Mandowara

March 16 (Reuters) - Advisers to the U.S. Food and Drug Administration on Thursday overwhelmingly backed full approval of Pfizer's oral antiviral COVID-19 treatment Paxlovid for adults at high risk of progression to severe disease.

The FDA's panel of outside experts voted 16-to-1 in favor of the drug's benefits outweighing its risk for some adults with mild-to-moderate COVID-19.

The agency is expected to make a formal approval decision by May and typically follows the advice of its expert advisers, but is not required to do so.

A full approval will eventually allow Pfizer to sell Paxlovid - which consists of two drugs in pill form - at market rates on the private market in the U.S., rather than through government contracts as it has been thus far.

Pfizer has sold the U.S. government nearly 24 million courses of Paxlovid at around $530 a course. As of March 12, the U.S. had distributed about 12.7 million courses and more than 8.5 million have been dispensed, according to government data.

A full approval also would provide doctors more flexibility in prescribing the drug and also allow the company to expand its advertising campaign.

Thursday's positive vote came after the FDA and Pfizer provided data assuaging concerns about the potential for a rebound in COVID symptoms after a five-day course of treatment.

Numerous anecdotal reports of a return of symptoms following Paxlovid treatment, including in high profile patients such as President Joe Biden and Dr. Anthony Fauci, had raised concerns.

Several panel members said they were reassured by the data presented on the COVID rebound issue.

Paxlovid has been authorized for emergency use in the U.S. in mild-to-moderate COVID patients aged 12 years and older since late 2021, but Pfizer's application for full approval only covers high-risk adults.

The FDA earlier on Thursday said the current Paxlovid emergency use authorization (EUA) for high-risk adolescents will continue to remain in effect even if it receives full approval for use in older patients. (Reporting by Leroy Leo and Khushi Mandowara in Bengaluru, Additional reporting by Michael Erman in New York; Editing by Krishna Chandra Eluri and Bill Berkrot)