The decade since the introduction of active immunization against poliomyelitis has seen not only a greater-than-90% reduction in the incidence of the disease but also a radical change in its epidemiological characteristics. Formerly, the illness had no respect for social class or place of residence; now, with rare exceptions, epidemics have been limited to sharply demarcated geographic areas occupied by economically depressed and ethnically isolated population groups.
The reason for this shift in epidemiological pattern is explained by the development of new and simplified methods of conducting immunization surveys.1 It is now possible to plan, conduct, and complete a survey for an entire city in less than two weeks. More than 100 such surveys conducted since 1958 have revealed the consistently sharp correlation of the level of immunization with socioeconomic status, particularly for the preschool age group. Recent outbreaks of poliomyelitis have occurred almost exclusively within poorly immunized populations. Thus,
SURVEYS OF IMMUNITY TO POLIOMYELITIS. JAMA. 1964;187(10):769–770. doi:10.1001/jama.1964.03060230097027