Congenital rubella syndrome due to infection after maternal antibody conversion with vaccine

We experienced a case of congenital rubella syndrome (CRS) due to infection after maternal antibody conversion with vaccine. The mother was immunized with rubella vaccine at 14 years of age, and was confirmed as having rubella-specific hemagglutination inhibition (HI) antibody at the 1:16 level both at ages 26 and 30 during preceding pregnancies. At the second week of the third gestation, her second child developed rubella. She did not suffer any symptoms, but was found to have rubella HI antibody at the 1:512 level at 9 weeks of gestation. She delivered a male baby weighing 2,545 g at 38 weeks of gestation. He had congenital pneumonia, patent ductus arteriosus, bilateral cataracts, sensorineural deafness, and periventricular calcification of the brain. The rubella-specific antibody was 1:512 by HI and 10.1 by IgM enzyme-linked immunosorbent assay. According to these observations, he was diagnosed as having CRS. The rubella virus genome was detected in the fluids of the vitreous body using RT-nested PCR. This case emphasizes the importance of double-dose immunization (once in infants and once in young adults) in order to obtain an adequate level of antibody with duration sufficient to ensure the prevention of CRS.