Polio Vaccine
Two polio vaccines are used throughout the world to combat polio. The first was invented by Jonas Salk, and first tested in 1952 and announced to the world by Salk on March 26, 1953. It consists of an injected dose of killed polio virus. Albert Sabin produced an oral polio vaccine using live but weakened virus in 1962.
The live-virus vaccine has the advantage that it can confer immunity on some people who do not themselves receive the vaccine, if they are closely exposed to a vaccinated person. It has the disadvantage that it can itself cause polio. In the United States, the use of live-virus vaccine was discontinued after 2000, but it is still used elsewhere.
The two vaccines have eliminated polio from most of the countries in the world and reduced early cases from hundreds of thousands per year to only 1000 worldwide in 2001.
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