In the informal survey, 80 percent said they thought Americans would need to wear masks in public indoor places for at least another year. Just 5 percent said people would no longer need to wear masks indoors by this summer. In large crowds outdoors, like at a concert or protest, 88 percent of the epidemiologists said it was necessary even for fully vaccinated people to wear masks. “Unless the vaccination rates increase to 80 or 90 percent over the next few months, we should wear masks in large public indoor settings,” said Vivian Towe, a program officer at the Patient-Centered Outcomes Research Institute.