Prevention of Haemophilus influenzae type b disease.

Haemophilus influenzae type b (Hib) is the leading cause of meningitis in children < 5 years of age. The majority of cases of Hib occur in infants < 2 years of age. Until recently the only vaccine available against this disease contained the pure polysaccharide (PRP) of Hib (Hib-PRP vaccine). The Hib-PRP vaccine was demonstrated to be efficacious in infants > 18 months of age but not below that age. This product was licensed for routine use in the USA for children aged 24 months or more. Recently a hyperimmune globulin termed bacterial polysaccharide immune globulin (BPIg) was prepared by immunizing adult donors with Hib-PRP, meningococcal and pneumococcal vaccines. BPIg has been demonstrated to prevent Hib infections when it is administered to infants at 4-month intervals. However, BPIg has not been licensed for routine use in the USA. A number of new Hib conjugate vaccines have also been developed in the last few years by convalently linking the Hib-PRP to different carrier proteins. Four different Hib conjugate vaccines have undergone clinical trials in the USA. Two of these vaccines, HbOC (Hib capsular oligosaccharide linked to CRM197) and Hib-OMPC (Hib capsular polysaccharide linked to Neisseria meningitidis outer membrane protein complex) have been demonstrated to protect infants aged 2 months or more from Hib disease. Both HbOC and Hib-OMPC are currently licensed for routine use in the USA. The widespread use of these vaccines should have a substantial impact in reducing morbidity and mortality from Hib disease.