What type of vaccine is used against H. influenzae type b?

• A. Live attenuated virus
• B. Conjugated capsular polysaccharide
• C. Inactivated pathogen
• D. Recombinant protein

Answer: (B)

The vaccine used against Haemophilus influenzae type b (Hib) is a conjugated capsular polysaccharide vaccine. This type of vaccine works by linking the polysaccharide capsule of the bacteria to a carrier protein, which enhances the immune response. The polysaccharide alone would not provoke a strong immune response, especially in young children, because polysaccharides are T-cell independent antigens. By conjugating this polysaccharide to a protein, the immune system can recognize the combined structure, allowing for the activation of T-cells and resulting in a more robust and long-lasting immune response.

This enhanced immune response includes the production of antibodies specific to the Hib bacteria, effectively protecting individuals from invasive diseases caused by this pathogen, such as meningitis and pneumonia. The use of a conjugated vaccine has been particularly successful in reducing the incidence of Hib infections, especially in children, who are at a higher risk for these severe diseases.

Other vaccine types listed, such as live attenuated virus, inactivated pathogen, and recombinant protein, refer to different approaches used for other pathogens and do not apply to the vaccine against H. influenzae type b, which specifically utilizes a conjugated capsular polysaccharide strategy for effective immunization.