Haemophilus influenzae b polysaccharide revaccination: a continued role for the unconjugated vaccine

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Haemophilus influenzae type b (Hib) polysaccharide vaccines are crucial for preventing invasive Hib disease.
• Understanding the long-term immune response to early Hib vaccination, including revaccination, is important for optimizing vaccination schedules.

Purpose of the Study:

• To investigate the effects of early primary vaccination with Haemophilus influenzae b polysaccharide vaccine on subsequent revaccination responses.
• To determine if early vaccination at 18-20 months induces immune priming (memory) or tolerance.

Main Methods:

• 36 children vaccinated at 18-20 months were stratified by antibody concentration and revaccinated at different ages (24-27, 30-33, or 36-39 months).
• Antibody concentrations were measured using radioantigen binding assay.
• Responses were compared to age-matched unvaccinated control groups.

Main Results:

• Post-reimmunization geometric mean antibody concentrations were 3.1, 3.0, and 7.8 µg/ml for the three revaccination groups.
• Antibody response rates (>1 µg/ml) were 75%, 80%, and 93%, respectively.
• These responses were comparable to age-matched unvaccinated controls.

Conclusions:

• Early primary vaccination with Hib polysaccharide vaccine does not appear to induce immune priming or tolerance.
• Revaccination responses are similar to primary responses in unvaccinated children, suggesting no benefit from early priming.
• Further research may be needed to understand optimal revaccination strategies for Hib.