Vaccines have eradicated smallpox, pushed polio to the verge of eradication, and saved millions of children from measles, diphtheria, tetanus, and other deadly and disabling diseases. Thanks in large part to the power of vaccines, the number of children dying before the age of five has fallen from 20 million in 1960 to 6.9 million in 2011, despite a large increase in global population.