Prevalence of antibodies against rubella virus in Spain.

The importance acquired by the strategy of anticipating rubella revacunation needs no emphasis1. Recommendations by experts committees and actualization of the prevailing childhood immunization schedules are unanimous when it comes to including the above-mentioned strategy2. In this context, seroepidemiologic survey studies allow the assesment of humoral immunologic response against viral structural antigens3,4 despite the assumed potential bias attached to their design. Being aware of the importance of describing rubella seropositivity real status in our setting we decided to document such situation in children under theoretically proper immunization schedules. The present contribution relies on data from a cross-sectional study carried out between 1999 and 2000 in children from the autonomous region of Spain, Castilla y León, (the largest region in the European Economic Community). The chosen framework was restricted to serum samples received in a Microbiology Laboratory of a University Hospital with the request of analyzing infectious markers other than rubella antibodies. According to demographic features a double stratification was made and we evaluated 323 children whose age was between 1 and 5 years and 1166 from 6 to 14 years of age. All samples were alicuoted and frozen (-20oC) until the moment of processing. Antibodies to proteic antigens of rubella viral envelope were determined by means of an indirect enzymeimmunoassay (EIA) (Bio-Whittaker, USA). Results were validated according to manufacturer's instructions and samples that showed a neat absorbance greater the cut-off value plus 15% were considered positive.