High incidence of adults with rubella antibody in northern Japan.

Abstract

A seroepidemiological study of rubella in northern Japan was made by testing for hemagglutinin-inhibitory (HAI) antibodies to rubella virus using an HAI test with our modification. An epidemic of exanthematous disease, which occurred in 1966–1967, was confirmed as rubella by the age specific distribution of rubella HAI antibody. However, one of the 14 areas tested in the region, a Piedmont village, was found to have had no rubella experience during the last 15 years. In general, a higher incidence of high titered HAI antibody was observed among the younger ages, suggesting a decrease of antibody titer with an increase in age after infection. Through these studies, it is evident that 100% of adults over 20 years of age possessed HAI antibody in all age groups and all areas so far examined. This fact may possibly explain the extremely rare incidence of congenital rubella syndrome in the northern part of Japan.