Prevention of measles in Israel: implications of a long-term partial immunization program

Following the introduction of routine measles immunization in Israel in 1967, rapid and persistent modifications in the pattern of the disease were observed, including much more limited and more widely spaced epidemics, a change in the age distribution of measles cases, and a progressively increasing herd immunity that was estimated, following the 1982 epidemic, at 91.6 percent for the first 26 generations. This pattern supports the expectation that measles can be eliminated in Israel provided a herd immunity greater than or equal to 94 percent can be achieved before the next epidemic, which is predicted for 1988-89. A logistic approach to the elimination of measles in Israel requires (a) maintenance of an immunization rate of at least 90 percent in each newborn generation; (b) identification and immunization of still susceptible children in the 1-5 year and 6-9 year age groups, to attain vaccination coverage for at least 97 percent of this population (which should result in immunity among at least 94 percent); (c) provision of similar coverage for older, susceptible individuals in selected groups of children, adolescents, and young adults at high risk; (d) disease surveillance based on an early identification of the main sources of infection and monitoring of the active foci of disease in the neighbouring territories, which are an important potential source of the introduction of infection.