The future of polio eradication.

As the global polio eradication initiative comes ever closer to its goal of terminating of all wild poliovirus transmission, significant challenges remain. Wild poliovirus transmission must be terminated in countries where low-level transmission persists, in large reservoir countries with high population density, and in conflict countries. Eradication can be achieved in these countries with determined and persistent effort, assuming that sufficient resources are mobilised. High quality surveillance needs to be implemented in the remaining polio endemic countries, especially in Africa. Surveillance is necessary in all countries until eradication is certified. A strategy for stopping immunisation after eradication is yet to be defined. A definition of this strategy would address the emergence of feral polioviruses, chronic vaccine virus infection in immunodeficient persons, and containment of laboratory strains. Until immunisation is stopped, high-population immunity should be maintained through uniformly high immunisation coverage with potent vaccines.