LONDON: Britain on Thursday became the first country in the world to approve a potentially game-changing COVID-19 antiviral pill jointly developed by U.S.-based Merck (MRK.N) and Ridgeback Biotherapeutics, in a boost to the fight against the pandemic.

Britain’s Medicines and Healthcare products Regulatory Agency (MHRA) recommended the drug, molnupiravir, for use in people with mild to moderate COVID-19 and at least one risk factor for developing severe illness, such as obesity, older age diabetes, and heart disease.

It will be administered as soon as possible following a positive COVID-19 test and within five days of the onset of symptoms, the regulator said, citing clinical data.

The green light is the first for an oral antiviral treatment for COVID-19 and the first for a COVID-19 drug that will be administered widely in the community. U.S. advisers will meet this month to vote on whether molnupiravir should be authorized.

Treatments to tackle the pandemic, which has killed more than 5.2 million people worldwide, have so far focused mainly on vaccines. Other options, including Gilead’s (GILD.O) infused antiviral remdesivir and generic steroid dexamethasone, are generally only given after a patient has been hospitalised.

Merck’s Molnupiravir has been closely watched since data last month showed it could halve the chances of dying or being hospitalised for those most at risk of developing severe COVID-19 when given early in the illness.

Molnupiravir, which will be branded as Lagevrio in Britain, is designed to introduce errors into the genetic code of the coronavirus that causes COVID-19 and is taken twice a day for five days.

Professor Stephen Powis, national medical director for the National Health Service (NHS) in England, said the drug would be administered to patients at higher risk of complications as Britain heads into one of the most challenging winters ever.

A wider rollout will follow if it is clinically and cost effective in reducing hospitalisations and death, he added.

“We are now working across government and the NHS to urgently get this treatment to patients initially through a national study so we can collect more data on how antivirals work in a mostly vaccinated population,” UK vaccines minister Maggie Throup told parliament.