New considerations for Haemophilus influenzae type b vaccination.

The immunogenicity, efficacy, adverse effects, dosage recommendations, and cost of the three commercially available Haemophilus influenzae type b (Hib) conjugate vaccines are discussed. Three Hib conjugate vaccines are licensed for use in children 15 months of age or older: ProHIBiT (Connaught), HibTITER (Praxis), and PedvaxHIB (Merck). HibTITER and PedvaxHIB were recently approved for use in infants as young as two months of age; both have demonstrated efficacy in preventing Hib disease in this age group, whereas ProHIBIT has not been shown to afford adequate protection in young infants. Because the three vaccines induce markedly different immunologic responses, they cannot be considered interchangeable and the recommended dosage schedules differ. The Centers for Disease Control Immunization Practices Advisory Committee (ACIP) and the American Academy of Pediatrics (AAP) both recommend that all infants be immunized with a complete series of either HibTITER or PedvaxHIB beginning routinely at two months or as soon as possible thereafter. The cost of a single dose is similar for the three Hib conjugate vaccines; full immunization with HibTITER is more expensive than with ProHIBiT or PedvaxHIB because four doses are required for completion of the series. Selection of the appropriate Hib vaccine for infants should be based on availability, cost, and the clinician's interpretation of existing data.