Measles in a partially immunized community.

During the investigation of a measles outbreak in a rural community, a spectrum of illness was observed which ranged in severity from a brief febrile illness to one characteristic of typical measles. Unimmunized children were more apt to develop measles (p less than 0.001) than were immunized children. However, a proportion of both the immunized and unimmunized children developed a milder, "measles-associated," illness. Employing a logistic model, it was demonstrated that the probability of developing either measles or "measles-associated" illness decreased with increasing age at immunization but was not affected by the interval since immunization.