1030 PASSIVE IMMUNIZATION OF INFANTS AGAINST HAEMOPHILUS INFLUENZAE TYPE B (HIB) BY MATERNAL VACCINATION

Abstract

Prior to a planned conception, 24 women were immunized with purified HIB capsular polysaccharide to attempt to extend their offspring's period of passive antibody protection against systemic HIB disease. All women had an antibody rise. Geometric mean titer prior to immunization was 1.2 μg/ml and at 1, 7-10, and 19-27 months after immunization was 35 μg/ml, 23 μg/ml, and 16 μg/ml respectively as measured by radioantigen binding. Most post-immunization antibody was of the IgG class as determined by an enzyme-linked immunosorbent assay. However, there was a wide range of post-immunization titers (2.7-310 μg/ml at 7-10 months post-immunization). The low magnitude antibody responders also had low IgG antibody levels that were not boostable. The offspring of 6 women, born 11½ to 17½ months after immunization, had antibody titers markedly higher than those of age-matched infants of unvaccinated women. Their titers persisted above the estimated protective level through 6-12 months of age. Four infants, all born to low-responder women, had titers similar to natural antibody titers. These results suggest that the interval of passive antibody protection can be extended. This approach may be especially useful in populations highly susceptible to HIB and may be applicable to the prevention of other childhood and neonatal infections.