Objectives. To analyze postvaccination serological status in pregnant women inadvertently vaccinated against rubella in the state of Rio de Janeiro, Brazil. Methods. This was a cross-sectional study of pregnant women 15 to 29 years old, vaccinated against rubella and measles from November 2001 to March 2002, who were unaware of their pregnancy at the time of vaccination or who became pregnant within 30 days thereafter. They were tested for rubella-specific immunoglobulin M (IgM) and G (IgG) and

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... classified as immune (IgM-negative, IgG-positive, tested within 30 days after vaccination), susceptible (IgM-positive after vaccination) or indeterminate (IgM-negative, IgG-positive, vaccinationserological testing interval greater than 30 days). Results. Of 2 292 women, 288 (12.6%) were susceptible, 316 (13.8%) immune, 1 576 (68.8%) indeterminate, 8 (0.3%) ineligible, and 104 (4.5%) lost to follow-up. IgM seropositivity by vaccination-serological testing interval was 16.1% (≤ 30 days), 15.4% (30-60 days), and 14.2% (61-90 days). Considering the campaign's target age, the 20-to-24-year age group had the largest proportion of individuals susceptible to rubella (14.8%) and represented 42.4% (122/288) of all susceptible women. In 75% of susceptible pregnant women, gestational age was 5 weeks or less at the time of vaccination. Conclusions. Mass immunization of childbearing-age women was justified on the basis of epidemiological and serological data. Follow-up of vaccinated pregnant women revealed no cases of congenital rubella syndrome due to rubella vaccination. However, the observed rate of congenital infection supports the recommendation to avoid vaccinating pregnant women, and to avoid conception for up to 1 month following rubella vaccination. ABSTRACT Rubella is usually a mild disease in childhood. However, the clinical and public health relevance of this disease is due to congenital rubella syndrome (CRS), which affects fetuses and newborns of mothers infected during pregnancy, mainly in the first trimester. Congenital rubella syndrome is a serious disease with high psychosocial costs, and requires specialized medical