Two types of polio vaccine are available: Oral Polio Vaccine (OPV) and Inactivated Polio Vaccine (IPV).
Ever since OPV was introduced, it has been the vaccine administered most extensively worldwide. However, almost all the industrialized countries are now using IPV. The main reason is to minimize the risk for Vaccine Associated Paralytic Polio (VAPP) incidentally caused by OPV. The rate of vaccine-associated paralytic poliomyelitis is generally about 1 case per 750,000 vaccine recipients. The risk is the highest for children receiving their first dose of OPV.
Sometime sequential use of IPV followed by OPV is preferred.