However, young and healthy patients, including children, and pregnant and breastfeeding women should not be given the drug due to 'potential harms', WHO experts say.

Merck says its pill has a mechanism that can work against Omicron and any other variant.

Merck's drug has been authorised to treat mild-to-moderate Covid-19 in adults who are at risk for severe disease.

The health ministry has also approved a request from Merck for a clinical trial import licence for its Covid-19 pill Molnupiravir.

The pill shows a 30% reduction in hospitalisations and deaths based on data from over 1,400 patients, compared to about 50% in October based on data from 775 patients.

Both drugs are being studied to see if they can prevent infection in people exposed to the virus.

Results for Pfizer's experimental anti-viral pill appear to surpass those seen with Merck & Co Inc's pill molnupiravir.

It will be administered as soon as possible following a positive Covid-19 test and within five days of the onset of symptoms.

The FDA is considering emergency use authorisation of the medicine, which was shown in a clinical trial to halve the risk of serious disease and death when given early for Covid-19.

Prime Minister Boris Johnson has removed almost all Covid-19 restrictions and is relying on vaccines and treatments to try and withstand winter pressures on hospitals.

The money will support efforts to develop and make generic versions of what could become the first oral antiviral medication for the disease if it wins regulatory approval.

The price is very low if compared with the US$700 per course that the US has agreed to pay for 1.7 million courses of Merck's molnupiravir pills.