The epidemiology and prevention of disease caused by Haemophilus influenzae type b.

Disease caused by H. influenzae type b is a world-wide problem of major proportions that affects both developed and developing countries. Young children are at particularly high risk of developing serious invasive infections. There has been tremendous recent progress in the development of vaccines that are immunogenic even in young infants. Clinical trials have demonstrated the efficacy of these polysaccharide-protein conjugate vaccines in infants. Two of these vaccines have been licensed in the United States for use in infants, and licensure of a third conjugate vaccine is expected soon. Many questions still remain to be answered. Are there significant differences in the efficacy for infants of the different licensed conjugate vaccines? Are the differences in the recommended schedules of immunization for the different vaccines justified? Would a combination of an initial dose of PRP-OMP (which is the most immunogenic vaccine in 2-month-old children) followed by subsequent doses of HbOC or PRP-T provide better overall protection than a schedule that uses only a single vaccine? Although much more research remains to be done, these vaccines, which have been recommended for routine universal immunization of infants in the United States, give us the capability of effectively preventing this potentially devastating infection of children.