The Global Polio Eradication Initiative (GPEI), launched 34 years ago, aimed to eradicate poliomyelitis by 2000. The chosen strategy was to stop circulation of wild polioviruses, following the successful example of smallpox eradication. The task, however, turned out to be much more challenging than eradicating smallpox had been, since there are hundreds of asymptomatic poliovirus infections for each paralytic case that occurs, which substantially complicates critical surveillance. Aside from challenges inherent in vaccine delivery in some countries, another reason for the failure to eradicate polio were outbreaks caused by circulating vaccine-derived poliovirus (cVDPV) strains that emerged from viruses used in Oral Polio Vaccine (OPV). Thus, to actually eradicate poliovirus, the use of OPV must also be stopped.