Seroprevalence of rubella antibodies in the State of Sao Paulo, Brazil, 8 years after the introduction of vaccine

Rubella vaccine was introduced in the official immunization calendar of the State of Sao Paulo, in 1992, at 15 months of age, following a mass vaccination targeting all children between 1 and 10 years of age. This mixed strategy was designed taking into account serological data and mathematical models to estimate the optimal ages for vaccination. To evaluate the efficacy of routine vaccination on rubella infection in Sao Jose do Rio Preto, State of Sao Paulo, 8 years after the introduction of vaccine, a seroprevalence survey was carried out in December 2000, comprising 1536 subjects aging from 6 months to 25 years. Rubella specific IgG was detected in blood samples by enzyme-linked immunosorbent assay (ELISA). From 18 months to 5 years of age (covered by a mass vaccination campaign 6 months before the Study) the seroprevalence was above 90%. From 6 to 8 years of age (vaccinated by routine schedule at 15 months), the seroprevalence was 76%. Front 9 to 18 years of age (vaccinated at the mass campaign that introduced the vaccine 8 years before) the seroprevalence was about 85%. After 20 years of age, protection was acquired by previous infection, as they were not covered by any vaccine program. From 20 to 25 years of age, the seroprevalence was 70%. As the seroprevalence remains low at ages not vaccinated, it should be expected low infection rates at this age window. Despite this, the present situation deserves care, as routine vaccination is given a protection below the minimum level necessary (80%). The efficacy of the proposed strategy depends on better routine vaccination coverage. A second dose of vaccine should also be considered. (C) 2003 Elsevier Science Ltd. All rights reserved.