Smallpox was a disease that has probably killed more than 500 million people. In many ways, the disease changed the course of history for nations that were overwhelmed by the infection or monarchs who were killed by it. The vaccine, which was invented in the late 1700s by Edward Jenner, has eliminated the disease from the face of the earth. This disease, which killed about 1 of every 3 people infected, and often left survivors blind, is now an historical footnote because of the vaccine. No story shows the power of vaccines more than this one.