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Response of 7- to 15-month-old infants to sequential immunization with Haemophilus influenzae type b-CRM197 conjugate
E P Rothstein1, R P Schiller, J A Girone
1Pennridge Pediatrics Associates, Sellersville, PA.
Insights
The Haemophilus influenzae type b oligosaccharide-CRM197 conjugate vaccine is highly immunogenic in infants. It primes the immune system, and polysaccharide vaccine can be used for boosting if needed.
Area of Science:
- Pediatric Immunology
- Vaccinology
- Infectious Disease Prevention
Background:
- Haemophilus influenzae type b (Hib) poses a significant threat to infants.
- Effective immunization strategies are crucial for preventing Hib infections in young children.
Purpose of the Study:
- To assess infant immune responses to Haemophilus influenzae type b polysaccharide vaccine after prior immunization with Hib oligosaccharide-CRM197 conjugate vaccine.
- To compare the immunogenicity of different Hib vaccination schedules in infants aged 7 to 15 months.
Main Methods:
- 171 infants aged 7–15 months were assigned to three groups with varying doses of Hib oligosaccharide-CRM197 conjugate vaccine and Hib polysaccharide vaccine.
- Immunizations were administered at 0, 2, and 6 months, with antibody levels measured at multiple time points up to 12 months.
Main Results:
- The Hib oligosaccharide-CRM197 conjugate vaccine demonstrated high immunogenicity, with geometric mean antibody levels of 31 and 35 µg/mL in different age groups.
- While Hib polysaccharide vaccine boosted antibody levels, it was less effective than the conjugate vaccine.
- Two doses of the conjugate vaccine led to sustained high antibody levels at 1 and 6 months post-immunization.
Conclusions:
- The Hib oligosaccharide-CRM197 conjugate vaccine effectively induces protective antibody levels and primes the infant immune system.
- The Hib polysaccharide vaccine can serve as a viable alternative for booster immunizations if required.
Objective:
To evaluate the immunologic potential of infants 7 to 15 months of age to respond to Haemophilus influenzae type b polysaccharide vaccine following immunization with H influenzae b oligosaccharide-CRM197 conjugate vaccine.
Study Design:
One hundred seventy-one infants, aged 7 to 15 months, were consecutively and alternatively assigned to one of three immunization protocols. Group 1 (n = 71) received three doses of H influenzae b oligosaccharide-CRM197 conjugate vaccine, group 2 (n = 47) received two doses of H influenzae b oligosaccharide-CRM197 conjugate vaccine followed by one dose of H influenzae type b polysaccharide vaccine, and group 3 received one dose of H influenzae b oligosaccharide-CRM197 conjugate vaccine followed by two doses of H influenzae type b polysaccharide vaccine. Immunizations were given on day 0 and at 2 months and 6 months. Anti-H influenzae type b polysaccharide antibody levels were measured on day 0 and 2, 3, 6, 7, and 12 months after the study began.
Results:
Haemophilus influenzae type b polysaccharide vaccine given as a second dose stimulated an antibody rise but did so less effectively than H influenzae b oligosaccharide-CRM197 conjugate vaccine. Two doses of H influenzae b oligosaccharide-CRM197 conjugate vaccine were highly immunogenic; geometric means were 31 and 35 micrograms/mL in the 7- to 11-month and 12- to 15-month age groups, respectively. Following two doses of H influenzae b oligosaccharide-CRM197 conjugate vaccine, both immunization protocols resulted in (1) equally high geometric mean antibody levels 1 month after immunization and (2) similar geometric mean antibody levels 6 months after immunization.
Conclusions:
Haemophilus influenzae b oligosaccharide-CRM197 conjugate vaccine induces antibody levels that would be expected to protect infants from initial invasion and primes the immune system for an anamnestic response. Our data indicate that if a booster immunization is needed, H influenzae type b polysaccharide vaccine could be an alternative to H influenzae b oligosaccharide-CRM197 conjugate vaccine.