Economic considerations for the eradication endgame.

An infectious disease will be eradicated only if it is eliminated everywhere, including in the hardest-to-reach, most vaccine-wary communities. If eradication is successful, it promises a dividend in the form of avoided infections and vaccinations. However, success is never certain unless and until eradication is achieved, and claiming the dividend means bearing the possibly great risk of re-emergence. Economic analysis of eradication evaluates these risks and rewards relative to the alternative of 'optimal control', and also exposes the incentives for achieving and capitalizing on eradication. Eradication is a 'game', because some countries may be willing to eliminate the disease within their borders only if assured that all others will eliminate the disease within their borders. International financing is also a game, because each country would rather free ride than contribute. Finally, for diseases such as polio, capitalizing on eradication is a game, for should any country continue to vaccinate in the post-eradication era using the live-attenuated polio vaccine, the countries that stop vaccinating will be exposed to the risk of vaccine-derived polioviruses. In the framework developed in this paper, eradication is a seductive goal, its attainment fraught with peril.