Routine and mass administration of oral polio vaccine (OPV) since 1961 has 
prevented many millions of cases of paralytic poliomyelitis. The public health 
value of this inexpensive and easily administered product has been 
extraordinary. Progress of the Global Polio Eradication Initiative has further 
defined the value of OPV as well as its risk through vaccine-associated 
paralytic poliomyelitis (VAPP) and vaccine-derived polioviruses (VDPV). Although 
both are rare, once wild poliovirus transmission has been interrupted by OPV, 
the only poliomyelitis due to poliovirus will be caused by OPV. Poliovirus will 
be eradicated only when OPV use is discontinued. This paradox provides a major 
incentive for eventually stopping polio immunization or replacing OPV, but it 
also introduces complexity into the process of identifying safe and 
scientifically sound strategies for doing so. The core post eradication 
immunization issues include the risk/benefits of continued OPV use, the extent 
of OPV replacement with IPV, possible strategies for discontinuing OPV, and the 
potential for development and licensure of a safe and effective replacement for 
OPV. Formulation of an informed post eradication immunization policy requires 
careful evaluation of polio epidemiology, surveillance capability, vaccine 
availability, laboratory containment, and the risks posed by the very tool 
responsible for successful interruption of wild poliovirus transmission.