Determination Of Protective Levels Of Maternal Antibody

Child Health And Human Development

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Abstract

This prospective seroepidemiology study was conducted in six academic centers from 1995 to 1999 to estimate the level of maternal antibody required to protect neonates against early-onset disease. Infants who developed early-onset group B streptococcal (GBS) disease ("cases") and infants who did not have GBS disease despite being surface colonized ("controls") were recruited. Maternal and cord sera were collected for antibody determinations. GBS isolated from blood, cerebral spinal fluid, and surface swabs of infants were serotyped. A total of 132 cases and 1638 controls were identified. Levels of IgG antibody to each GBS type will be determined. Analyses of maternal serum IgG GBS Ia antibodies, measured by ELISA in 45 cases caused by GBS type Ia and 319 controls (neonates colonized by GBS Ia but without GBS disease) showed that neonates whose mothers had IgG anti-GBS Ia equal or greater to 5 microgram per mililiter (g/ml) had an 88% lower risk of developing type-specific early-onset disease compared with neonates whose mothers had levels less than 5 microgram/ml. An additional study was conducted to evaluate the effectiveness of risk-based intrapartum antibiotics prophylaxis (IAP) in prevention of early-onset GBS disease. Infants with early-onset disease ("cases") and infants without GBS disease ("controls") were selected from infants born to mothers with one or more risk factors to GBS disease. We analyzed 109 cases and 207 controls. Nineteen (17%) of case and 69 (33%) of control mothers received IAP. In adjusted analyses, the effectiveness of IAP in preventing early-onset GBS disease was 86%.