Fetal-neonatal passive immunization against Hemophilus influenzae, type b.

Twenty-one pregnant women were vaccinated with the polyribophosphate capsular antigen of Hemophilus influenzae, type b, at 34 to 36 weeks of gestation. All women experienced a large boost in their own antibody levels of anti-polyribophosphate capsular antigen, and 30% was transferred to their newborn infants. The newborn serum anti-polyribophosphate capsular antigen level at birth was 100-fold greater than that of control newborn infants, and the antibody persisted at a protective level for 12 months. Since newborn infants lose significant antibody by 3 months of age, they are susceptible to infection by Hemophilus influenzae, type b, such that it is the leading cause of meningitis in infants. The passive levels of anti-polyribophosphate capsular antigen achieved in these fetuses-neonates by active immunization of their mothers should theoretically lead to less disease caused by Hemophilus influenzae, type b, during infancy.