effective in extinguishing outbreaks in the past and therefore is the expected strategy for containing outbreaks in the post-OPV era (CDC 2005a). However, recent responses to cVDPV outbreaks have occurred in a well-immunized surrounding population, and this would continue to be true in the first years after OPV use has ceased. Models suggest that massive local intervention with mOPV would be capable of ending an outbreak without leaving enough susceptible people to sustain new chains of transmission (Duintjer Tebbens et al. 2005). Workshop discussions were not detailed enough to allow the committee to rigorously evaluate the models on which current eradication plans are based, but the committee believes that there are still too many unknowns to predict with certainty how the post-eradication scenario will unfold. The recent discovery of an iVDPV in five unvaccinated Amish children in Minnesota, 6 years after the discontinuation of OPV use in the United States and in the face of nearly universal vaccination with IPV in the surrounding population, suggests that the last chains of transmission of vaccine strains will be difficult to detect and terminate (CDC 2005b).