Abstract
In September-October 1985, a measles outbreak occurred among elementary school students on a small offshore island near Taiwan. The outbreak began with nosocomial transmission of measles in a hospital emergency room on the main island of Taiwan. Four distinct generations of transmission occurred among elementary school children and their household contacts. Elementary school children were susceptible to measles because they were born after the last major outbreak, but before measles vaccine was locally available. Low immunization rates and low vaccine efficacy contributed to the spread of measles among preschool-age household contacts.