Before the introduction of the first polio vaccine in 1955, polio (poliomyelitis) caused thousands of cases of paralysis. Despite widespread immunization with oral vaccine since 1962, polio persists in some nations in Asia and Africa. There are 2 forms of the vaccine: an oral form containing live, attenuated poliovirus (oral poliovirus vaccine [OPV], Sabin vaccine); and an injectable form containing killed virus (inactivated poliovirus vaccine [IPV], Salk vaccine), which is administered subcutaneously. To eliminate the risk of vaccine-associated paralytic poliomyelitis, a condition that has been associated more often with OPV than with IPV, only IPV is used in the United States. Because OPV is cheaper and easier to distribute and because it transmits the virus to unimmunized contacts of those who are vaccinated, helping the former develop immunity, the WHO suggests that OPV be used for immunization in developing countries. The currently used bivalent OPV is less likely to cause vaccine-associated polio than the older trivalent form. OPV is contraindicated in pregnant women or immunosuppressed patients, who should receive only the inactivated virus vaccine.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.