Watch NOVA Season 42 Online

Diseases that were largely eradicated in the United States a generation ago—whooping cough, measles, mumps—are returning, in part because nervous parents are skipping their children’s shots. NOVA’s “Vaccines—Calling the Shots" takes viewers around the world to track epidemics, explore the science behind vaccinations, hear from parents wrestling with vaccine-related questions, and shed light on the risks of opting out.