Congenital rubella syndrome despite maternal antibodies.

A congenital rubella syndrome (Box 1) is rare in Canada, it does still occur. Many women immigrate to Canada from countries without a rubella vaccination program and may not have adequate immunity. In 2002, only 124 (58%) of 214 countries or territories around the world had implemented a rubella vaccination program. An Australian study found that women born in Asia, sub-Saharan Africa and South America were 5 times as likely as other women to be seronegative for rubella virus. In a review of all cases of infants with congenital rubella syndrome in the United States reported to the National Congenital Rubella Syndrome Registry from 1997 to 1999, 83% (20/24) were born to Hispanic mothers and 91% (21/23) were born to foreignborn mothers. Sri Lanka does not have a rubella vaccination program; therefore, if our patient’s low positive titre from 1993 was a true-positive result, it was likely the result of natural immunity. Since serologic testing for rubella was documented only once preceding this pregnancy, we strongly suspect, but cannot confirm, that this case of congenital rubella syndrome resulted from rubella reinfection: the IgG titre had increased markedly, from 17 IU/mL in 1993 to 281 IU/mL 10 years later, with a positive IgM titre and no history of revaccination. A rubella-specific IgM test performed at 12 weeks’ gestation would have confirmed infection rather than immunity. Numerous cases of congenital rubella syndrome due to rubella reinfection have been reported. All involved exposure to rubella in the first trimester of pregnancy after both natural and vaccine-induced immunity, usually with subclinical infection in the mother. The immune response may involve more than humoral immunity, but it is clear that rubella antibodies decline over time and may increase the risk of reinfection. In a study involving Korean children, 18.8% of those who had been vaccinated and 13.8% of those with natural immunity were found to be seronegative for rubella virus after 3 years. An TEACHING CASE REPORT