Two polio vaccines are used throughout the world to combat polio. The first was developed by Jonas Salk, first tested in 1952, and announced to the world by Salk on April 12, 1955. It consists of an injected dose of inactivated (dead ) poliovirus. Thereafter, Albert Sabin produced an oral polio vaccine using attenuated poliovirus. Human trials of Sabin's vaccine began in 1957 and it was licensed in 1962. The two vaccines have eradicated polio from most of the countries in the world and reduced the worldwide incidence from an estimated 350,000 cases in 1988 to fewer than 2000 cases in 2006. (wikipedia)