Haemophilus influenzae type b capsular polysaccharide (PRP) conjugate (Hib conjugate vaccine)

The vaccine carrier protein covalently conjugated to polyribosylribitol phosphate (PRP) is the immunogenic component of Haemophilus influenzae type b (Hib) conjugate vaccines (Pichichero, 2013). PRP is the capsular polysaccharide of the Hib bacterium, which acts as a primary virulence factor by preventing phagocytosis (CDC, 2022). In its pure form, PRP is a T-cell independent antigen that fails to elicit a strong immune response or memory in infants (Pollard et al., 2009). By covalently linking PRP to a carrier protein—such as tetanus toxoid, diphtheria toxoid, or CRM197—the complex is transformed into a T-cell dependent antigen (StatPearls, 2023). This allows the vaccine to be processed by antigen-presenting cells and recognized by T-helper cells, which in turn stimulate B-cells to produce high-affinity IgG antibodies and establish long-term immunological memory (WHO, 2013). These conjugate vaccines have been instrumental in reducing the incidence of invasive Hib diseases, including bacterial meningitis, pneumonia, and epiglottitis, globally (CDC, 2022).

Other names

PRP-TPRP-DPRP-OMPHbOCPolyribosylribitol phosphate conjugateHib vaccine

Induces active immunity by converting a T-cell independent polysaccharide antigen into a T-cell dependent antigen through covalent linkage to a carrier protein, stimulating anti-PRP IgG production (StatPearls, 2023).