“The antiviral Lagevrio (molnupiravir) is safe and effective at reducing the risk of hospitalisation and death in people with mild to moderate Covid-19 who are at increased risk of developing severe disease,” the UK government said in a statement on Thursday.

The drug, developed by Florida-based firm Ridgeback Biotherapeutics and US pharmaceutical giant Merck, passed a “rigorous review” by UK regulators and the government’s independent expert advisory body.

Health Secretary Sajid Javid said the “ground-breaking” treatment will be “a game changer for the most vulnerable and the immunosuppressed,” describing it as “an excellent addition to our armoury against Covid-19.”

Molnupiravir is named after Norse god Thor’s hammer, Mjolnir.

Munir Pirmohamed, the chair of the Commission on Human Medicines, said the clinical trials has shown that the drug reduces the risk of hospitalisation or death for at-risk adults with mild to moderate Covid-19 by 50%.