Childhood vaccines have transformed medicine. Smallpox has been globally eradicated, polio has been eliminated from the U.S., and diphtheria and congenital rubella have been almost wiped out in North America. Yet some preventable diseases—most notably measles—are managing to make a comeback in certain pockets of the U.S. after a small number of parents have refused to give their children routine immunizations. In the article leading this section, a pediatrician and an epidemiologist detail how intentionally unvaccinated children are helping drive epidemics. And once misinformation takes hold, it can be hard to dispel—especially the thoroughly debunked work linking certain inoculations with autism, as Scientific American staff editor Dina Fine Maron writes in the next piece. She takes on the "facts or fiction" about vaccination risks. In the final piece of the section, Scientific American staff editor Mark Fischetti illustrates how, although vaccination rates for U.S. children were slipping before 2011, many school immunization laws seem to be having a positive effect. Remaining gaps in vaccination coverage leave community members who are ineligible for vaccines—including adults who have weak immune systems and babies who are too young to get their shots—vulnerable to potentially life-threatening disease.