Vaccine-associated "wild-type" measles.

Measles is the most contagious of the childhood exanthems and is the leading cause of vaccine-preventable deaths in children, mostly in developing countries. The prodromal stage, consisting of high fever and the triad of cough, coryza, and conjunctivitis, is followed by a caudal progressing rash over a period of 2 to 3 days. With a worldwide vaccination program in place, mortality and morbidity have decreased substantially. Receipt of the live attenuated vaccine generally causes no or only mild side effects such as a low-grade fever and a subtle rash. We report a 1-year-old boy who, 10 days after vaccination, developed vaccine measles which was clinically indistinguishable from the natural disease. Vaccine virus was detected by polymerase chain reaction in the patient's nasopharyngeal secretions.