The polio vaccine was developed in 1955 by Dr. Jonas Salk and thus called the “Salk vaccine”. It is the inactivated or killed vaccine that was given by intramuscular injection but now it is given orally. The inactivated polio vaccine produces antibodies in the blood to all three types of poliovirus. In the event of infection, these antibodies prevent the spread of the virus to the central nervous system and protect against paralysis.