The development of vaccines has changed modern history by preventing diseases that once killed millions of people. But there have recently been outbreaks of childhood maladies thought to have been eliminated. Most Americans don't remember measles, because the disease was declared eradicated in the year 2000. But, from New York to California, recent outbreaks are reminders of the potentially deadly disease, due to a drop in the vaccination of vulnerable children. Elsewhere in the world, polio's making a comeback, where violence and religious beliefs have discouraged vaccination or made it impossible. In America, some parents are making a choice. Is there a lack of trust in the public health system? Are the media spreading misinformation? How's a parent to know?