• Vaccine Name: ProHIBiT
• Target Pathogen: Haemophilus influenzae
• Target Disease: Meningitis
• Product Name: H. influenzae type b conjugate vaccine (PRP-D)
• Tradename: ProHIBiT
• Vaccine Ontology ID: VO_0000660
• Type: conjugate vaccines
• Antigen: Haemophilus b capsular polyribosyl-ribitol-phosphate(PRP)-diphtheria toxoid (D)
• Preparation: ProHIBiT was prepared from the purified capsular polysaccharide, a polymer of ribose, ribitol and phosphate (PRP) of the Eagen Haemophilus influenzaetype b strain covalently bound to diphtheria toxoid (D) and dissolved in sodium phosphate buffered isotonic sodium chloride solution. The polysaccharide- protein conjugate molecule is referred to as PRP- D. Thimerosal (mercury derivative) 1:10,000 is added as a preservative. The vaccine is a clear, colorless solution. Each single dose of 0.5 mL is formulated to contain 25 µg of purified capsular polysaccharide and 18 µg of diphtheria toxoid protein (ProHIBiT 2007).
• Description: The manufacturing process utilizes a technology of covalent bonding the capsular polysaccharide of Haemophilus influenzae type b to diphtheria toxoid, to produce an antigen which is postulated to convert a T- independent antigen into a T- dependent antigen. The protein carries both its own antigenic determinants and those of the covalently bound polysaccharide. As a result of the conjugation to protein, the polysaccharide is presented as a T- dependent antigen resulting in both an enhanced antibody response and an immunologic memory (Lepow et al., 1987).

Human Response

• Vaccination Protocol: ProHIBiT ® is indicated for immunization against invasive diseases caused by Haemophilus influenzae type b. ProHIBiT ® may be administered as a booster vaccination at 12 to 15 months of age in children who received primary immunization with Haemophilus b Conjugate Vaccine (Meningococcal Protein Conjugate) or Haemophilus b Conjugate Vaccine (Diphtheria CRM 197 Protein Conjugate). This vaccine also may be administered as primary immunization at 15 months of age in children who have not received primary immunization with any licensed Haemophilus b Conjugate Vaccine (AAPC 1991). The immunizing dose is a single injection of 0.5 mL given intramuscularly in the outer aspect area of the vastus lateralis (mid- thigh) or deltoid.
• Immune Response: In studies conducted with ProHIBiT ® in several locations throughout the US, the antibody responses of 18- to 26- month- old children were measured, mean antibody levels induced by ProHIBiT ® in children 18 to 20 months of age are 30- fold higher than those induced by polysaccharide vaccines in the same age group. Following immunization of 16 to 24- month- old children with a single dose of ProHIBiT ® , 89% (109/ 123) had antibody levels ³ 0.15 µg/ mL 12 months post- immunization, compared to 93% one month post- immunization (ProHIBiT 2007).
• Side Effects: Side effects associated with a single vaccination of HibTITER include fever, local reactions, rash, diarrhea , vomiting , prolonged crying.