Molecular size characterization of Haemophilus influenzae type b polysaccharide-protein conjugate vaccines

Current vaccines against Haemophilus influenzae type b (Hib) consist of capsular polysaccharide, polyribosylribitol phosphate (PRP), chemically conjugated to a carrier protein. The stability of the conjugate is essential for vaccine efficacy, as the target population for this vaccine includes infants, who do not mount an immune response to free polysaccharide vaccines. A method has been developed for determining structural stability and batch-to-batch consistency of Hib vaccines by the application of fast protein liquid chromatography (FPLC). This FPLC method is fast, reproducible, and can be used to evaluate single human doses of Hib vaccines. We have shown that the FPLC elution profiles provide a suitable indicator of vaccine stability under normal and degradative conditions. The method may also be applicable to other conjugate vaccines such as meningococcal and pneumococcal protein-polysaccharide conjugates.