The U.S. Food and Drug Administration is poised to authorize a pair of pills from Pfizer Inc. and Merck & Co. to treat COVID-19 as soon as this week, according to people familiar with the matter -- a milestone in the fight against the pandemic that will soon expand therapies for the ill.

An announcement may come as early as Wednesday, according to three of the people. They asked not to be identified ahead of the authorization and cautioned that the plan could change. 

Pfizer’s pill, Paxlovid, and Merck’s molnupiravir are intended for higher-risk people who test positive for the coronavirus. The treatments, in which patients take a series of pills at home over several days, could ease the burden on stretched hospitals with infections poised to soar through the winter in the U.S. 

The FDA declined to comment. 

“It’s the biggest thing to happen in the pandemic after vaccines,” said Eric Topol, director of the Scripps Research Translational Institute. The timing of the announcement, so late in the year, is unusual for the FDA and reflects the urgency behind the medicines, he added.

The FDA authorizations may come with limitations on who should get which drugs., one of the people familiar with the matter said. A Food and Drug Administration advisory committee narrowly recommended the Merck pill last month, with some members of the panel citing safety concerns including for pregnant women.

Pfizer closed at US$58.95 a share in New York, down about 3.4 per cent, while Merck closed at US$75.54, down about 1.1 per cent.

White House Press Secretary Jen Psaki said she wouldn’t get ahead of any FDA decision. 

“But certainly, having antivirals available is another component that will help us fight the virus, address the pandemic, help people return to a version of normal and we will be prepared like Boy Scouts and Girl Scouts to ensure we are making these antivirals available to the public,” she said Tuesday.

President Joe Biden, speaking at the White House on Tuesday about the omicron variant, said the current spike in cases is not like previous surges because of the availability of medical supplies and vaccines. He warned of increasing breakthrough cases in vaccinated people but assured Americans that almost of all of them would be mild or entirely asymptomatic.

“No, this is not March of 2020,” he said.

The U.S. government has ordered 10 million courses of the Pfizer pill and about 3 million courses of Merck’s, which isn’t as effective, clinical studies indicate, and may carry risks. However, the pills are likely to not be immediately available in widespread supply.

In a clinical trial, Pfizer’s pill showed an 89 per cent reduction in hospitalization for patients who received the medicine within three days of developing symptoms, compared to patients who got a placebo. None of the patients treated with the drug died. 

Authorization for Pfizer’s pill would represent a vote of confidence in the medicine from regulators, as FDA advisers have not been asked to consider the drug’s clinical evidence.

Merck developed molnupiravir with partner Ridgeback Biotherapeutics LP.