Feb 2, 2015 7:50 PM EDT

A measles outbreak has reached 14 states and infected more than 100 people. The disease had been considered eradicated in the U.S., but parents’ skepticism about the safety and usefulness of vaccines in recent years has made room for measles to spread. In a story for Retro Report, the NewsHour Weekend’s Zachary Green considers the roots of the vaccine debate. (Watch More at pbs.org)