CDC revises policy to recommend vaccinated people wear masks in certain indoor settings, including schools Window decals at Southold Elementary School last September warn visitors that masks must be worn in the building. (Credit: Grant Parpan) Vaccinated people should resume wearing masks in public, indoor settings — including schools — to help prevent the spread of COVID-19, according to an updated interim guidance announced Tuesday by the Centers for Disease Control and Prevention. The new guidance applies to counties that have either “substantial” or “high” level of transmission. Suffolk County is currently listed as “substantial” level of transmission, as is Nassau County and most of New York City. Nearly all upstate counties in New York are listed at either low or moderate.