Postvaccine era measles epidemiology.

Measles incidence in the United States was calculated from estimates of the United States Immunization Survey for the years 1965 to 1975. These data were examined according to birth cohorts and cross-sectionally by age to determine the effect of live measles virus vaccine on measles epidemiology. The results showed a high rate of infection for children aged 1 year, followed by a decrease in the infection rates for preschool children, with rates increasing agin at ages 5 and 6 years. It was hypothesized that an effective vaccine-induced herb immunity exists in preschool children until they are of school age. When incidence rates were based on susceptible children, the highest rates occurred in the school-aged populations.