The Delta variant is more contagious. It does not appear to be more severe.

“As far as anyone can tell, Delta isn’t more dangerous in the sense that it causes worse disease,” Wurtz told me. “It’s a sneaky opportunist, not a mayhem man.”

Janet Baseman, a University of Washington epidemiologist, said: “I have not seen compelling evidence that the Delta variant is more severe.” Dr. Paul Sax of Brigham and Women’s Hospital in Boston told me, “This sense of greater disease severity is more anecdotal than driven by actual data.” Dr. Eric Topol of Scripps Research said, “I don’t think it makes kids sicker.”

Dr. Aaron Richterman of the University of Pennsylvania said that he did not think Delta required vaccinated parents to behave differently than they did a few weeks ago. Richterman has young children himself, and his family has not changed its behavior, he said.