In 2010, California suffered the largest and deadliest outbreak of pertussis, also known as ''whooping cough,'' in more than fifty years. This tragedy was avoidable. An effective vaccine has been available since the 1940s. In recent years other diseases, like measles and mumps, have also made a comeback. The reason for these epidemics can be traced to a group whose vocal proponents insist, despite evidence to the contrary, that vaccines are poison. As a consequence, parents and caretakers are rejecting vaccines for themselves and their families.In ''Deadly Choices,'' infectious-disease expert Paul Offit takes a look behind the curtain of the anti-vaccine movement. What he finds is a reminder of the power of scientific knowledge, and the harm we risk if we ignore it.