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Depression of anticapsular antibody after immunization with Haemophilus influenzae type b polysaccharide-diphtheria
C D Marchant1, E Band, J E Froeschle
1Department of Pediatrics, St. Boniface General Hospital, Winnipeg, Canada.
Insights
Immunization with Haemophilus influenzae type b conjugate vaccine can temporarily lower antibody levels in infants. This temporary dip in antibodies may increase the risk of infection shortly after vaccination.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Invasive Haemophilus influenzae type b (Hib) infections pose a significant risk to infants.
- Capsular polysaccharide vaccines are used to prevent Hib infections.
- Concerns exist regarding the timing of Hib infections post-vaccination.
Purpose of the Study:
- To investigate the effect of Haemophilus influenzae type b capsular polysaccharide-diphtheria conjugate vaccine on infant antibody concentrations.
- To document any temporary depression of anticapsular antibodies following immunization.
Main Methods:
- Study involved 18-month-old infants receiving Hib conjugate vaccine.
- Antibody concentrations were measured before and at specific intervals (Day 2, Day 7) post-immunization.
- Statistical analysis was performed to assess antibody level changes.
Main Results:
- Infants with detectable pre-immunization antibodies showed a significant depression of antibody concentrations by Day 2 (P = 0.002).
- By Day 7, all infants achieved protective antibody levels (>0.15 µg/ml).
- However, 33% of infants without detectable pre-immunization antibodies did not reach protective levels by Day 7.
Conclusions:
- Haemophilus influenzae type b conjugate vaccine can cause a transient depression in anticapsular antibody concentrations in infants.
- This temporary reduction in antibody levels, along with potential failure to develop adequate antibodies, may contribute to post-vaccination Hib infections.
- Further research is needed to understand the mechanisms behind antibody depression, possibly involving antibody binding to the vaccine.
Abstract:
Invasive Haemophilus influenzae type b infections have been observed in the week after immunization with capsular polysaccharide vaccine. We sought to document depression of antibody concentrations after immunization of 18-month-old infants with H. influenzae type b capsular polysaccharide-diphtheria conjugate vaccine. All 9 infants with detectable preimmunization anticapsular antibody had depression of antibody concentrations on the second day after immunization (P = 0.002). By Day 7 all had achieved anticapsular antibody concentrations greater than 0.15 micrograms/ml, a level believed to provide protection to immediate challenge with H. influenzae type b. Of those without detectable preimmunization antibody, 7 of 21 (33%; 95% confidence interval, 11 to 56%) had not achieved concentrations of greater than 0.15 mg/ml 1 week after immunization. We conclude that there is depression of anticapsular antibody concentrations during the first week after immunization with H. influenzae type b capsular polysaccharide-diphtheria conjugate vaccine. We speculate that H. influenzae type b infections after immunization with H. influenzae type b vaccines may be the result of: (1) low antibody concentrations because of either depression of antibody concentrations or failure to develop antibody; and (2) exposure to H. influenzae type b. Depression of antibody concentrations could be explained by binding of in vivo antibody to the vaccine.