Safety and immunogenicity of Haemophilus influenzae type B polysaccharide-diphtheria toxoid conjugate vaccine in adults.

Sixty-one adults received either Haemophilus influenzae type b capsular polyribosephosphate (PRP) vaccine or H. influenzae type b polysaccharide-diphtheria toxoid conjugate (PRP-D) vaccine in two doses, one month apart. Both vaccines were well tolerated with no fever or systemic reactions. There were no significant local reactions. Mild local tenderness was reported by about half of the subjects in both groups. There was no observed effect of the vaccines on hematologic parameters, including reticulocyte and platelet counts, evaluated before immunization, one month after the first dose, and seven to 10 days after the second dose. A single dose of PRP-D induced levels of IgG antibody to PRP three times that observed with PRP alone one month after the first inoculation.