Hib vaccines are made from capsular polysaccharide that has been extracted from cultures of Hib bacteria. The polysaccharide is linked (conjugated) to a protein to increase the immunogenicity, especially in young children, in whom the plain polysaccharide vaccines are not immunogenic.

Hib conjugate vaccine exists as a monovalent vaccine or as a component of several combined vaccines e.g. DTwP/Hib, DTaP/IPV/Hib  (used in the infant primary immunisation programmes) and Hib/MenC (a booster vaccine given at 12 months of age).

Hib and Hib-containing vaccines are released into the EU market and are analysed as part of the batch release process. Hib tests include: visual inspection, endotoxin content, molecular size, polysaccharide and protein identities, total and free polysaccharides, using physico-chemical and immunological assays.

NIBSC reference standards are used in the immunological  and physico-chemical characterisation of Hib vaccines.