When Georgia Moore (second from left) was diagnosed with leukemia in 2010, her parents, Trevor and Courtney Moore, worried about the germs her younger sister, Ivy, would bring home from school.
Courtesy of the Moore family/Kaiser Health News
A boy stands in line for a measles vaccination in the northern Central African Republic. More than half the cases of measles each year are reported in Africa and Asia.
Spencer Platt/Getty Images
Leah Russin, of Palo Alto, Calif., holds her son, Leo, 16 months, as she speaks Wednesday at a news conference in support of proposed state legislation that would require parents to vaccinate all school children.