Merck expects to produce 10 million courses of the molnupiravir treatment by the end of this year, with at least 20 million set to be manufactured in 2022. (Photo: Reuters)

Britain's Medicines and Healthcare products Regulatory Agency 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.

US advisers will meet at the end of this month to review the drug's safety and efficacy data and vote on whether molnupiravir should be authorized. 

The pill 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.