Polio as it is commonly known is an acute, viral, infectious disease spread from person to person, primarily via the fecal-oral route. An inflammation of the spinal cord’s grey matter, although a severe infection can extend into the brainstem and even higher structures, resulting in polioencephalitis, producing apnea that requires mechanical assistance such as an iron lung.
Poliomyelitis was first recognized as a distinct condition by Jakob Heine in 1840. Its causative agent, poliovirus, was identified in 1908 by Karl Landsteiner. Although major polio epidemics were unknown before the late 19th century, polio was one of the most dreaded childhood diseases of the 20th century. Developed in the 1950s, polio vaccines have reduced the global number of polio cases per year from many hundreds of thousands to under a thousand today.Two polio vaccines are used throughout the world to combat poliomyelitis.
The first candidate polio vaccine, based on one serotype of a live but attenuated virus, was developed by the virologist Hilary Koprowski. Koprowski’s prototype vaccine was given to an eight-year-old boy on February 27, 1950. Koprowski continued to work on the vaccine throughout the 1950s, leading to large-scale trials in the then Belgian Congo and the vaccination of seven million children in Poland against serotypes PV1 and PV3 between 1958 and 1960.
The second inactivated virus vaccine was developed in 1952 by Jonas Salk at the University of Pittsburgh, and announced to the world on April 12, 1955. The Salk vaccine, or inactivated poliovirus vaccine (IPV), is based on poliovirus grown in a type of monkey kidney tissue culture (vero cell line), which is chemically inactivated with formalin After two doses of IPV (given by injection), 90% or more of individuals develop protective antibody to all three serotypes of poliovirus, and at least 99% are immune to poliovirus following three doses.
It consists of an injected dose of inactivated (dead) poliovirus. An oral vaccine was developed by Albert Sabin in 1957 and it was licensed in 1962. The two vaccines have eradicated polio from most countries in the world, and reduced the worldwide incidence from an estimated 350,000 cases in 1988 to 1,652 cases in 2000.