The agency’s data suggest that people with weak immune systems should wear masks even in places that do not have high transmission of the virus. File Photograph: iStock

The Delta variant is much more contagious, more likely to break through protections afforded by the vaccines and may cause more severe disease than al(...)

People queue at a Covid-19  testing site at Gonzales Park in Compton, California, on Sunday. Photograph: Philip Cheung/New York Times

California compelled much of the state to close shop on Monday and New York ordered hospitals to increase bed capacity by 25 per cent, as the United S(...)