Gestational exposure to rubella vaccinees: a population surveillance study

Over a two-year period an attempt was made to identify instances of transmission of rubella vaccine virus from rubella vaccinees to pregnant women in Nashville-Davidson County, Tennessee. Approximately 24,000 children were immunized in a mass campaign at the outset of the study. Several prospective surveillance methods of 11,635 women and their new babies were employed. Attempts were made to recover rubella virus from throat swabs of 10,951 newborns. No rubella vaccine virus was recovered. Wild rubella virus was isolated from a single infant with the congenital rubella syndrome whose mother had natural rubella during the first month of pregnancy. Rubella virus was not isolated from the products of 240 abortions. There were no seroconversions among 3990 women who had paired sera available for study. Clinical and serologic follow-ups of infants judged to be a high risk because of intimate maternal exposure to vaccine virus revealed no late manifestations of congenital rubella infection. A history of close maternal contact with vaccinees during the three months before and the three months following conception was not associated with an increased incidence of congenital anomalies or clinical features seen with congenital rubella infection. Thus, no evidence of vaccine virus transmission was found, providing further evidence of the safety of rubella vaccine under field conditions. A seroepidemiologic study of 8824 pregnant women revealed the expected decline in rubella susceptibility with increasing age. When age was controlled, the variables of race, parity, and educational achievement produced no major influence on immunity.