An anonymous reader quotes a report from Ars Technica: With firm vaccination campaigns, the US eliminated measles in 2000. The highly infectious virus was no longer constantly present in the country -- no longer endemic. Since then, measles has only popped up when travelers carried it in, spurring mostly small outbreaks -- ranging from a few dozen to a few hundred cases each year -- that then fizzle out. But all that may be about to change. With the rise of non-medical vaccine exemptions and delays, the country is backsliding toward endemic measles, Stanford and Baylor College of Medicine researchers warn this week. With extensive disease modeling, the researchers make clear just how close we are to seeing explosive, perhaps unshakeable, outbreaks. According to results the researchers published in JAMA Pediatrics, a mere five-percent slip in measles-mumps-and-rubella (MMR) vaccination rates among kids aged two to 11 would triple measles cases in this age group and cost $2.1 million in public healthcare costs. And that's just a small slice of the disease transmission outlook. Kids two to 11 years old only make up about 30 percent of the measles cases in current outbreaks. The number of cases would be much larger if the researchers had sufficient data to model the social mixing and immunization status of adults, teens, and infants under two.