New science has again prompted the Centers for Disease Control and Prevention to update its mask guidelines. The CDC recommended on Tuesday that fully vaccinated people wear masks in public indoor settings "in areas with substantial and high transmission." That includes a large swath of the US right now, including the vast majority of counties in the South. The CDC recommended that all teachers, staff, students, and visitors at K-12 schools mask up as well. The goal of these new guidelines, CDC director Rochelle Walensky said, is to "help prevent the spread of the Delta variant and protect others." The...