Monica Gandhi, a professor of medicine at the University of California, San Francisco, and associate chief of its infectious disease division, said in an email that with vaccine authorization for children 5 to 11, “it makes most sense to me to lift mask mandates in schools (and for adults) once children have the ability to get both doses of the vaccine” — which, in an ideal world, likely means around eight weeks after shots become widely available. Gandhi said, “I am a firm believer in positive motivation and messaging and think making this metric explicit will convince more parents to vaccinate their children.”

Marr, the engineering professor, tweeted that two weeks after school restarts in January should be the earliest date under consideration, because children may pick up the usual non-Covid bugs during the holidays. She also said that she liked the idea of data-driven mask policies based on the level of virus spread in communities. Some experts, like Aaron Carroll, a professor of pediatrics and the chief health officer at Indiana University, was wary of setting specific dates, in case another highly infectious variant like Delta hits.