Biological activity of Hib conjugates

Haemophilus influenzae type b (Hib) conjugate vaccines dramatically improve the immunogenicity against the capsular polysaccharide (PRP) of Hib. A new Hib conjugate, PedvaxHIB, is shown to be immunogenic in infant rhesus monkeys. The monkey model appears to correlate well with the immunogenicity of PedvaxHIB in human clinical studies. Not all commercial Hib conjugates are immunogenic in the monkey model. The data from the priming study indicate that HibTITER is not immunogenic in an immune system naive to diphtheria toxoid, such as the infant rhesus monkey. The role of diphtheria toxoid in the immunogenicity of HibTITER in human infants should be studied.