Prospective comparison of the immune response of infants to three Haemophilus influenzae type b vaccines

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Haemophilus influenzae type b (Hib) infections pose a significant health risk, particularly in infants.
• Various Hib vaccines exist, including polysaccharide and conjugate formulations, with differing immunogenicity.
• Understanding the antibody response, including isotype distribution, is crucial for evaluating vaccine efficacy.

Purpose of the Study:

• To compare the antibody response elicited by three Haemophilus influenzae type b vaccines in infants.
• To analyze the isotype distribution of antibodies, specifically IgG1 and IgG2, following vaccination.
• To evaluate the immunogenicity of a polysaccharide vaccine (PRP) versus two conjugate vaccines (PRP-D and HbOC).

Main Methods:

• A study involving 134 infants aged 17 to 22 months.
• Sera collection before and 1 month after vaccination with purified H. influenzae type b capsular polysaccharide (PRP), PRP-D, or HbOC.
• Quantification of antibody response (≥1.0 µg/ml) and analysis of antibody isotype distribution (IgG1:IgG2 ratio).

Main Results:

• The HbOC vaccine induced a significantly higher antibody response (96%) compared to the PRP-D vaccine (72%).
• All vaccines resulted in higher IgG1 than IgG2 concentrations, with HbOC showing a significantly higher IgG1:IgG2 ratio.
• The IgG1:IgG2 ratio was comparable between PRP and PRP-D vaccines.

Conclusions:

• The HbOC conjugate vaccine demonstrates superior immunogenicity in infants compared to the PRP-D conjugate vaccine.
• While antibody isotype profiles were similar, HbOC elicited a more pronounced IgG1 response relative to IgG2.
• Further research is needed to determine the clinical significance of these observed differences in antibody responses.