Polio vaccination: past, present and future.

Live attenuated oral polio vaccine (OPV) and inactivated polio vaccine (IPV) are the tools being used to achieve eradication of wild polio virus. Because OPV can rarely cause paralysis and generate revertant polio strains, IPV will have to replace OPV after eradication of wild polio virus is certified to sustain eradication of all polioviruses. However, uncertainties remain related to IPV's ability to induce intestinal immunity in populations where fecal-oral transmission is predominant. Although substantial effectiveness and safety data exist on the use and delivery of OPV and IPV, several new research initiatives are currently underway to fill specific knowledge gaps to inform future vaccination policies that would assure polio is eradicated and eradication is maintained.