Social behavior

Europe has recorded a 60 percent drop in new coronavirus infections over the past month, the World Health Organization said Thursday, encouraging news that comes as the continent plans to reopen its borders. Still, “this progress is fragile,” a top agency official cautioned.

Schools in the U.S. should continue to use masks, C.D.C. advises.

The Centers for Disease Control and Prevention on Saturday clarified coronavirus advice for U.S. schools, recommending the continued, universal use of masks and physical distancing, after the agency’s sudden announcement that vaccinated Americans could forego masks indoors.

All schools teaching students from kindergarten through grade 12 should continue to implement proper mask-wearing through the end of the 2020-2021 school year, the C.D.C. said. The agency also kept in place its suggestions to observe physical distancing and to test for coronavirus infections.