The state of polio vaccination in the world: the case for continuing routine vaccination.

This article reviews the literature concerning polio vaccination and uses that information to evaluate the World Health Organization's announced plans to end polio vaccination early in the 21st century. The safe elimination of polio vaccination would require the elimination of all polio cases, including paralytic cases, mild, nonparalytic cases, and vaccine-associated cases; proof that polio does not have any nonhuman alternative host; proof that no one alive can still shed the poliovirus; proof that no poliovirus persists in the environment; and proof that no live poliovirus, either the wild type or the vaccine strain, exists in medical or terrorist hands. Because it does not seem possible to ensure that ending vaccination against polio would be safe, and given the fact the polio is a terrible and untreatable disease, it would seem prudent to continue polio vaccination for the foreseeable future.