Before there was an understanding of infectious disease, few weapons were available to fight it. Disease Warriors chronicles the groundbreaking work of early researchers, such as the famed scientist Louis Pasteur, who unmasked germs as the source of illness. Pasteur went on to develop a rabies vaccine — a great scientific triumph. Today, vaccines have made huge strides against epidemics, conquering smallpox and bringing the global eradication of polio within reach. But the world still faces major challenges in getting basic vaccines to those who still need them, and in creating new ones to combat modern nemeses, like AIDS.