Compare and contrast the two polio vaccines used to nearly eradicate polio.

Both vaccines are effective in providing immunity to all three strains of the polio virus, and both require booster vaccinations for complete immunity.

The first vaccine was developed by Jonas Salk in 1955 and is an inactivated polio vaccine (IPV). The Salk vaccine is inexpensive, is very stable in storage, and must be administered by injection. It poses no risk of causing disease.

Albert Sabin developed an alternative vaccine known as the oral polio vaccine (OPV), which is a live, attenuated vaccine. It is easier to administer (it is administered orally), but it is more expensive to prepare and is less stable in storage than the IPV. However, it can cause disease if administered to an immunocompromised person. The vaccine is a live, infectious agent, and people who have received the vaccine shed virus into the environment. There are two consequences of this property. On the one hand, the OPV can provide contact immunity, which is beneficial in areas where the polio incidence is high and vaccinating the entire population would be difficult for health care workers. On the other hand, the live vaccine can mutate to regain virulence and cause outbreaks of polio. One well-documented case of a polio outbreak caused by vaccine reversion occurred in 2001. For this reason, OPV use should be phased out as polio rates decline in a population.