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Haemophilus influenzae b polysaccharide revaccination: a continued role for the unconjugated vaccine
M E Pichichero1, A Bracikowski, R Sullivan
1Department of Pediatrics, University of Rochester Medical Center, NY 14642.
Insights
Early Haemophilus influenzae type b polysaccharide vaccination did not prime or induce tolerance. Revaccination responses in children were similar to those not previously vaccinated, indicating no immune memory.
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.
Abstract:
In a study of the issue of revaccination with Haemophilus influenzae b polysaccharide vaccine, 36 children who had been vaccinated with polysaccharide vaccine at age 18 to 20 months were stratified according to their 3-week postvaccination anticapsular antibody concentration determined by radioantigen binding assay, then sequentially assigned to one of three groups so as to have comparable distributions of peak antibody concentrations. These children were revaccinated with polysaccharide vaccine at 24 to 27, 30 to 33, or 36 to 39 months of age. The post-reimmunization geometric mean antibody concentrations in these three groups were 3.1, 3.0 and 7.8 micrograms/ml, respectively, and the percentages rising to greater than 1 microgram/ml were 75, 80 and 93%. The geometric means and antibody response rates were nearly identical to age-matched control groups not previously vaccinated. Thus there was no evidence of priming (memory induction) or of tolerance induction by the early (18 months old) primary vaccination.