Antibody responses in adult volunteers to pneumococcal polysaccharide types 19F and 19A administered singly and in combination.

The immunogenicity of the two major group 19 pneumococcal polysaccharides, types 19F and 19A, was studied in human volunteers. Antibody responses after vaccination with either 50 micrograms of type 19F polysaccharide, 50 micrograms of type 19A polysaccharide, or 25 micrograms of both polysaccharides premixed in a single injection revealed that the combined vaccine was immunogenic for both types, but that the optimal immunogen for each was the homologous polysaccharide. We concluded that vaccination with type 19F polysaccharide antigen, included in the current pneumococcal vaccine, does not induce a satisfactory heteroimmunogenic response to type 19A.