The U.K. approves Merck’s molnupiravir, making it the first pill to be endorsed for treating Covid.

Britain on Thursday approved the antiviral drug molnupiravir for treating the coronavirus, making it the first pill to be endorsed for Covid patients. The country’s regulatory body said that the antiviral pill, originally designed to fight the flu, was “safe and effective” in reducing the risk of hospitalization and death for those at increased risk of severe symptoms, according to a statement.

The decision was made after a “rigorous review” of its “safety, quality and effectiveness,” according to the statement from the regulatory body, the Medicines and Healthcare Products Regulatory Agency.

Clinical trial data has suggested that the pill is most effective when taken during the early stages of infection.

Sajid Javid, the British health secretary, described the approval as a “historic day” for his country. “This will be a game changer for the most vulnerable and the immunosuppressed, who will soon be able to receive the groundbreaking treatment,” he said.