There was a time when the measles were common enough to be a source of comedy on TV shows like "The Flintstones." So how did we go from joking about the measles to reports on the news about a growing international measles emergency? In the second episode of our "Infectious" series, we embark on a search for truth, aided by a renowned pediatrician and several prominent anti-vaccine activists. Along the way, we look at how vaccines actually work, fallout from the swine flu pandemic, and the highly controversial -- but unproven -- link between vaccines and autism.