Seroepidemiologic studies on rubella in Fukuoka in southern Japan during 1965-1981: rubella epidemic pattern, endemicity and immunity gap.

The epidemiology of rubella in most areas of Asia has not been defined. In Fukuoka city in southern Japan, rubella epidemics occurred in 1956-58, in 1966 and in 1976-77. During the first halves of the 1960s and 1970s, neither epidemic nor endemic clinical rubella occurred. Rubella mass vaccination for girls of 14 years of age started in 1978. Rubella seroepidemiologic studies were performed in 1965, 1974, 1978-79 and 1981 in Fukuoka city. Current studies indicated that children of 6-10 years of age during the epidemics of 1956-58, 1966 and 1976-77 were infected with rubella in 72%, 37% and 57% of cases, respectively. Just before the epidemics of 1966 and 1976-77 100% of the children under nine years of age had no antibodies to rubella indicating absence of recent outbreaks. Whereas 95% of the population (young women of 15-18 years of age in 1981) which participated in the rubella mass vaccination programme since 1978 have rubella Hl antibodies, 46% of the nonparticipating population (19-23 years of age in 1981) remains susceptible to rubella. These facts indicate that rubella epidemics occurred in 1956-58, 1966 and 1976-77, that the magnitude of each epidemic was different, and that there were intervals without endemicity in the inter-epidemic periods. However, after the nation wide rubella epidemic in 1975-77, endemic rubella continued, and rubella epidemics again occurred in 1980-82. The unique rubella epidemic pattern in Japan may be changing in the 1980s to that which existed in most areas of the world where rubella was endemic with periodic increased incidence of epidemicity.(ABSTRACT TRUNCATED AT 250 WORDS)