Maternal immunization with the capsular polysaccharide vaccine for Haemophilus influenzae type b

Maternal immunization with the capsular polysaccharide (PRP) vaccine of Haemophilus influenzae type b has been shown to extend the time that protective levels of maternal antibody are detected in infants. In a randomized, blinded trial, PRP or placebo was administered uneventfully to 213 women in the third trimester of pregnancy. Infants born to PRP recipients had significantly higher levels of antibody to PRP than did infants born to placebo recipients: 2.73 micrograms/ml compared with 0.33 microgram/ml. It was estimated that infants of mothers who received the PRP vaccine would be protected for an average of 4 months compared to an average of only 2 months for those of mothers who received placebo. Infants were followed for invasive H. influenzae type b disease through the first year of life; none was detected.