Poliomyelitis is a viral disease. The virus enters through the mouth and multiplies in the throat and gastrointestinal tract then moves into the bloodstream and is carried to the central nervous system where it replicates and destroys the motor neuron cells of the spinal cord resulting in paralysis, even death.There are three types of poliovirus: 1, 2, and 3. Type 1 is the most virulent and common. Type 2 poliovirus has not been detected anywhere in the world since 1999.
A vaccine tricks the body’s immune system into producing antibodies to fight a form of the virus that is not harmful. Then, if the person ever encounters the real and dangerous virus, the body is ready to prevent it from harming any cells.
From the early 1900s, researchers pursued two different kinds of polio vaccines. One used inactivated (killed) viruses. The other kind used live but attenuated or weakened, virus. Jonas Salk was the leading proponent of the killed virus and Albert Sabin became the foremost proponent of the attenuated virus approach.
Inactivated Polio Vaccine
This was first introduced in 1955 and is produced from wild-type poliovirus strains of each serotype that have been inactivated (killed) with formalin. Adverse events following administration of IPV are very mild and transient, and because it is a killed vaccine, there is no risk of the live-virus-associated risks.
Oral Polio Vaccine
This was first introduced in 1961 and consists of a mixture of the three live attenuated poliovirus serotypes (Sabin types 1, 2 and 3), selected for their lower neurovirulence and reduced transmissibility. In 2009, 2 bivalent (type-1 and type-3) OPVs (OPVs) were licensed. The mOPVs and OPVs are used primarily during mass campaigns. In the end-stages of stopping endemic transmission, monovalent OPV containing only attenuated virus of one serotype has been increasingly employed to target areas where one serotype predominates. Three or more spaced doses of OPV normally generate a protective immune response against subsequent infections, although in countries like ours additional doses (seven or more) may be required to prevent paralytic disease.
So we can say polio vaccine in use is both inactivated ie, IPV and live attenuated virus ie, OPV.