Safety and immunogenicity of a new Haemophilus influenzae type b vaccine in infants under one year of age

ABSTRACT

64 healthy infants, 2-3 months old, were randomly assigned to one of three vaccination groups which either diphtheria-pertussis-tetanus (DPT) vaccine, Haemophilus influenzae type b capsular polysaccharide polyribosyl-ribitol phosphate (PRP) vaccine, or PRP+P (with pertussis adjuvant) vaccine in three doses at intervals of two months. Local and systemic reactions occurred most frequently after DPT vaccination and least frequently for PRP alone. Data for 60 infants from whom complete sera sets were available indicated that 70 percent of the infants who received three doses of PRP+P showed two fold or greater increases in titers of antibody to PRP with final values above the level assumed to give protection against invasive H. influenzae type b disease (>0.15 ug/ml). In contrast, less than 10 percent of infants who received PRP vaccine alone showed 2-fold or greater increases (Summary)