One of the critical top five advancements in health care in the United states is the cure for polio. Polio was maiming and killing thousands of children (and many adults, like Franklin Delano Roosevelt) every year. Jonas Salk developed the vaccine and tested it beginning in 1952. It was introduced across the country, dispensed at neighborhood Fire Stations, in 1955. A vaccine operates on the principle of inoculation: a small amount of the disease is introduced so that natural antibodies of defense build up against it making the person thenceforth immune to contracting the disease.