A polysaccharide-protein complex from Haemophilus influenzae type b. III. Vaccine trial in human adults.

Polysaccharide-protein complex prepared from Haemophilus influenzae type b strain Eagan was evaluated for toxicity and immunogenicity in adult volunteers given intramuscular injection. Most subjects had moderate local inflammation that was maximal the day after vaccination. No lot of vaccine significantly exceeded a saline placebo in production of systemic symptoms. Neither the local nor the systemic reactions of individual subjects appeared to be related to prevaccination serum antibody titers. Serum antibody responses to the capsular polysaccharide (polyribosylribitolphosphate [PRP]) component were detected in approximately 80% of the subjects. The PRP content of the vaccine antigens varied, and the rate and extent of responses were as expected for an equivalent dose of purified PRP vaccine. Antibody responses were not enhanced by aluminum phosphate. There was no booster response to a second injection given after six months. Responses to the residual lipopolysaccharide component occurred in 80% of the subjects, primarily in the IgG class. Responses to the nonlipopolysaccharide somatic components were detected less frequently.