Children under 12 are not yet eligible for a COVID-19 vaccine, which both leaves them vulnerable to the virus and means there still will be outbreaks this upcoming school year, said Beth Carlton, an assistant professor of environmental and occupational health at the Colorado School of Public Health. Since it is possible the virus will be circulating in schools, other measures to reduce transmission — masking, physical distancing and adequate ventilation — will likely still be needed, she said.