In this episode: the roots of the modern anti-vaccine movement, and of the fears that still fuel it – from a botched polio vaccine, to the discredited autism study, to today. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia, and a professor of pediatrics at the University of Pennsylvania School of Medicine Arthur Allen, senior correspondent for nonprofit KFF Health News and author of Vaccine: The Controversial Story of Medicine's Greatest Lifesaver