Studies for both of these vaccines are starting to look at how effective and safe they are in children, but it will take several more months before researchers know more about how they perform in people as young as 12, said Dr. Jessica Cataldi, a pediatrician at Children’s Hospital Colorado [and assistant professor of pediatrics at CU School of Medicine] who specializes in infectious diseases. “We want to make sure that the vaccines are safe for kids because kids do have different immune systems,” she said.