Seven-year follow-up study of rubella syndrome in Ryukyu with special reference to persistence of rubella hemagglutination inhibition antibodies.

Rubella hemagglutination inhibition (HI) antibodies in 266 children with rubella syndrome born in 1965 in the Ryukyu Islands and their mothers were followed for seven years. Titers of rubella HI antibody in the mothers declined slowly, while those in the children declined rapidly up to 40 months of age. Thereafter decline of titers became extremely slow and only seven cases (three per cent) became seronegative for rubella HI antibody. Rubella HI antibody titers seemed to have no particular correlation to the severity of clinical manifestations.