Epidemic measles in a highly immunized rural West African (Gambian) village.

A measles epidemic occurred in a rural West African village, despite documented immunization in 90% of the less than 10-year age group. In contrast to previous epidemics, this outbreak caused no associated deaths among the 54 cases diagnosed. Immunization protected against infection--only 3.6% of immunized children developed measles, whereas 30.1% of those not immunized became ill (P less than .001). Thus, the vaccine efficacy rate was 90.1%. The average age at presentation was 72 months, and older patients were more likely to have severe disease. Nutritional status had no effect on susceptibility to measles infection or on outcome; weight loss (350 +/- 170 g) was most marked during the prodromal phase in young children. Infection was more severe when more than one case was diagnosed in a household (P less than .05) and in conditions of overcrowding, which were also associated with higher infection rates (P less than .02). Although immunization did not stop the spread of the epidemic within the village, a strict quarantine in the medical clinic probably prevented spread to other villages.