Cases of measles are rare in Massachusetts and Connecticut, but Emory University researchers say nationally one in eight children under the age of seventeen are at risk of infection.

Outbreaks are mostly prevented by what’s called herd immunity. According to the Department of Public Health, several Massachusetts counties remain undervaccinated, including Hampshire and Franklin.

“The real risk at this moment inside the state is low,” Sean Palfrey, a pediatrician at Boston Medical Center, says. “The risk of having an unimmunized child come to the state, because we have an awful lot of travelling going on, is 100 percent.”

Ninety-five percent of Massachusetts kindergartners have been vaccinated, while the rate is 97 percent in Connecticut.