A trend has been observed after decades of widespread vaccination of the occurrence of disease incidence in an older age group. Whereas measles would only affect children under the age of 10 in previous decades it is now routinely affecting adolescents and young adults. These are just a couple of papers highlighting this trend.

K. H. Rand, R. W. Emmons and T. C. Merigan. Measles in adults. An unforeseen consequence of immunization? JAMA Vol. 236 No. 9, August 30, 1976.

An outbreak of measles occurred in California in the first half of 1975, especially in the San Francisco Bay area. Of four adult patients with complicated cases, two were receiving immunosuppressive chemotherapy, and both died from a giant-cell pneumonia. The clinical presentation in such cases may be atypical, and special viral isolation and immunofluorescent techniques may be diagnostically helpful. A significant (P less than .0005) trend toward the occurrence of measles in adolescents was observed in this epidemic, which may also occur in future epidemics elsewhere. With wide spread but incomplete immunization, it is possible for the nonimmunized to reach adulthood without acquiring natural infection. As a result, internists as well as pediatricians will have to consider the possibility of measles and be aware of its serious potential in the immunosuppressed patient.

Cherry JD. The 'new' epidemiology of measles and rubella. Hosp Pract. 1980 Jul;15(7):49-57.

Both diseases have been effectively controlled in the pediatric population that, in the prevaccine era, harbored them. However, with the shift in prevalence to adolescents and young adults, it is possible the diseases may be "time bombs."