Just a day after the world's first approval of Merck & Co. Inc.'s oral antiviral for COVID-19 positioned it to offer a new way to keep Britons at high risk of severe disease out of the hospital, Pfizer Inc. is stopping a phase II/III trial of its oral antiviral, Paxlovid, early for "overwhelming efficacy" in a similar group. Interim results showed that combining the drug, also known as PF-07321332, with ritonavir reduced the risk of hospitalization or death for adults with mild to moderate COVID-19 but at high risk of severe disease by 89% vs. placebo.