Xocova (ensitrelvir) has been approved for COVID-19 prevention in Japan on the basis of promising trial results. Credit: The Yomiuri Shimbun via AP Images/Alamy An antiviral pill has, for the first time, been shown to prevent COVID-19 in people exposed to the SARS-CoV-2 virus at home, according to trial results published today in the New England Journal of Medicine 1 . The drug could be a lifeline for those who still face real danger from the virus, such as care-home residents or transplant recipients on immune-suppressing medication. The advance arrives years after the peak of the COVID-19 pandemic, so the real-world impact might be felt by only a narrow band of individuals. Still, “as a 78-year-old with comorbidities, I certainly would use it if I had a known exposure”, says study co-author Frederick Hayden, a clinical virologist at the University of Virginia School of Medicine in Charlottesville. Antiviral antidote The drug, called ensitrelvir , is made by the Japanese pharmaceutical company Shionogi.…