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Prevention of Haemophilus influenzae type b infections in Apache and Navajo children
M Santosham1, B Rivin, M Wolff
1Center for American Indian and Alaskan Native Health, Department of International Health, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
Insights
Haemophilus influenzae type b (Hib) vaccines were evaluated in high-risk Native American populations. PRP-OMP demonstrated high efficacy, even after a single dose, offering significant protection against Hib disease.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Immunology
Background:
- Haemophilus influenzae type b (Hib) disease surveillance initiated in 1981 among White Mountain Apache and Navajo populations.
- Hib disease attack rates in children under 5 were 5-10 times higher than in the general US population.
Purpose of the Study:
- To evaluate the immunogenicity and efficacy of three different Hib vaccines.
- To assess vaccine responses in high-risk pediatric populations.
Main Methods:
- Prospective surveillance of Hib disease.
- Evaluation of unconjugated polysaccharide, HbOC, and PRP-OMP Hib vaccines.
- Measurement of antibody responses and assessment of vaccine efficacy in Navajo and Apache infants.
Main Results:
- Unconjugated Hib polysaccharide showed lower antibody responses in Apache infants compared to white infants.
- HbOC induced lower initial responses in Navajo infants but achieved protective levels after three doses.
- PRP-OMP elicited strong immune responses in 2-month-old Navajo and Apache infants after a single dose and was over 90% efficacious.
Conclusions:
- PRP-OMP vaccine is highly efficacious in preventing Hib disease in Navajo infants, with significant protection even from a single dose.
- Vaccine effectiveness varied among different Hib vaccine formulations in these high-risk populations.
Abstract:
Prospective surveillance of Haemophilus influenzae type b (Hib) disease has been done since 1981 in two high-risk populations, White Mountain Apaches and Navajos. The attack rate in children less than 5 years of age is 5-10 times higher than in the general US population. Three vaccines were evaluated. Unconjugated Hib capsular polysaccharide produced lower antibody responses in 18- and 24-month-old Apache infants than in white infants. HbOC (Hib oligosaccharide covalently linked to the nontoxic mutant diphtheria toxin CRM197) produced low antibody responses in Navajo infants after one or two doses but induced responses similar to those in whites after three doses. The responses of 18-month-old Navajos to HbOC were lower than those of whites, but most achieved protective levels. PRP-OMP (Hib capsular polysaccharide linked to the outer membrane protein complex of Neisseria meningitidis) produced good immune responses in 2-month-old Navajo and Apache infants after a single dose. This vaccine was greater than 90% efficacious in protecting Navajo infants from Hib disease when given at 2 and 4 months of age. Even a single dose achieved a high protective efficacy.