Describes how, before the advent of vaccines, epidemics of measles, mumps, whooping cough, polio, and other crippling diseases ravaged humanity around the globe, and how that began to change when medical researchers developed the first vaccines, using a portion of a disease germ to stimulate the body's immune reaction. Today, hundreds of millions of people gain immunity to deadly diseases through vaccination.

The miracle at Melun -- Flickers of hope in a disease-ravaged world -- Discovering how the immune system works -- Triumph over a host of deadly maladies -- A modern backlash against vaccination -- New research and the future of vaccines.