The seroepidemiology of rubella: the independent analysis of current prevalence and past incidence in serological surveys in Spain.

Epidemiological patterns of rubella transmission were studied by performing haemagglutination-inhibition (HI) tests on 1 132 sera collected from urban and rural areas of Spain in the period 1969-71. Different epidemiological values were ascribed to 3 levels of HI titre in order to analyse current prevalence and past incidence independently. Titres below 8 were considered negative, while low titres (8-32) were taken to indicate old immunity, medium titres (64-512) to indicate well-established immunity, and high titres (>/=1 024) to indicate recent infection. The method appears to be of value for the surveillance of rubella. The findings confirmed that transmission takes place mainly among children of school age and continues at a substantial level up to about 30 years of age. The pattern of transmission differed markedly between city and rural populations.