In the U.S., enthusiasm on the right is building for so-called herd immunity, as the public grows skeptical of coronavirus vaccines. These developments could dash hopes for containing Covid-19 in the months ahead.Proponents of herd immunity say exposing more people to the coronavirus will build protection broadly in the population. But experts say that will result in many more illnesses and deaths, and that vaccines are a safer route to herd immunity. Emma Court reports that the concept gained traction in the White House, due to the increasing influence of Trump medical advisor Scott Atlas. It was backed this month by a group of academics in a treatise titled the Great Barrington Declaration.See omnystudio.com/listener for privacy information.