SINCE the isolation of the rubella virus in 1962,1,2 extensive research has been directed toward the development of a safe, effective vaccine. Several live attenuated vaccine strains have been developed and tested for safety, immunogenicity, and communicability in the United States and Europe.3-7 An island-wide epidemic of rubella on Taiwan, beginning early in 1968, provided the first opportunity for the evaluation of the clinical efficacy of some of these vaccines. Unlike other large populations, rubella is not endemic on Taiwan: island-wide epidemics are known to have occurred in 1944 and 1957 to 1958 with complete absence of disease in the intervening years.8 Those born since the latter epidemic were shown to be serologically susceptible shortly before the beginning of the 1968 epidemic,9 which began in northern Taiwan and spread rapidly southward with variable but generally high attack rates.
Earlier studies in northern Taiwan schoolboys with one