This experiment has already occurred in the former Soviet Union. In the turmoil of the early 1990s, the public health system failed to continue its mass vaccination program. Subsequently, the newly independent countries experienced an epidemic of diphtheria. While most modern countries have a rate of less than ten cases a year, these countries had an average of fifteen thousand cases a year in the 1990s, with an average of five hundred deaths annually. So if we stopped vaccinating against diphtheria, we too might experience such an epidemic.