Explanation:

• Polio vaccine, preparation of poliovirus given to prevent polio, an infectious disease of the nervous system.
• The first polio vaccine, known as inactivated poliovirus vaccine (IPV) or Salk vaccine, was developed in the early 1950s by American physician Jonas Salk. This vaccine contains killed virus and is given by injection. The large-scale use of IPV began in February 1954, when it was administered to American schoolchildren.
• In the following years, the incidence of polio in the United States fell from 18 cases per 100,000 people to fewer than 2 per 100,000.
• In the 1960s a second type of polio vaccine, known as oral poliovirus vaccine (OPV) or Sabin vaccine, named for its inventor American physician and microbiologist Albert Sabin, was developed. OPV contains live attenuated (weakened) virus and is given orally.