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Passive immunization for infection with Haemophilus influenzae type b
M Santosham1, R Reid, G W Letson
1Dept. of International Health, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
Insights
Haemophilus influenzae type b (Hib) meningitis affects high-risk infants. New conjugate vaccines show promise, but efficacy varies across populations, necessitating alternative protection strategies for vulnerable infants.
Area of Science:
- Pediatrics
- Immunology
- Infectious Diseases
Background:
- Haemophilus influenzae type b (Hib) is a primary cause of meningitis in US children under 5.
- Hib infection rates are 10-20 times higher in specific populations like Apache, Navajo, and Alaskan Eskimo children.
- Hib infections disproportionately affect infants, with over 80% occurring in the first year of life.
Purpose of the Study:
- To evaluate an alternative approach for protecting high-risk infants against Haemophilus influenzae type b infections.
- To address the limitations of current Hib vaccines in infants under 18 months.
- To investigate the efficacy of new conjugate Hib vaccines in diverse populations.
Main Methods:
- Clinical evaluation of novel Haemophilus influenzae type b vaccines.
- Preparation of vaccines by covalently coupling Hib capsular polysaccharide with a protein carrier antigen.
- Efficacy trials in different infant populations, including Finnish and Alaskan Eskimo infants.
Main Results:
- One conjugate Hib vaccine proved efficacious in Finnish infants immunized at 3, 4, and 6 months.
- The same conjugate vaccine was not efficacious in preventing Hib disease in Alaskan Eskimo infants under 1 year of age.
- Current licensed Hib vaccines lack reliable immunogenicity in infants younger than 18 months.
Conclusions:
- There is a need for alternative strategies to protect high-risk infants from Haemophilus influenzae type b.
- Vaccine efficacy for Hib may vary significantly between different infant populations.
- Further research is required to develop effective Hib vaccines for all infant populations.
Abstract:
Haemophilus influenzae type b is the leading cause of meningitis in children younger than 5 years of age in the United States. The incidence of infection with H influenzae type b in certain populations, such as Apache and Navajo Indians and Alaskan Eskimos, is 10 to 20 times higher than in the general US population. Another important feature of H influenzae type b infections in these populations is that more than 80% of the cases occur during the first year of life, with 35% to 45% occurring during the first 6 months. One of the currently licensed vaccines that contains the capsular polysaccharide of the H influenzae type b organism is not reliably immunogenic in infants younger than 18 months of age. A number of new H influenzae type b vaccines prepared by covalently coupling the H influenzae type b capsular polysaccharide with a protein carrier antigen are undergoing clinical evaluation. One of these conjugate vaccines was shown to be efficacious in preventing disease caused by H influenzae type b in Finnish infants when they were immunized at 3, 4, and 6 months of age. Unfortunately, in a recently concluded trial, the same vaccine was not found to be efficacious in preventing such disease in infants younger than 1 year of age among the Alaskan Eskimo population. We have evaluated an alternative approach for protecting high-risk infants.(ABSTRACT TRUNCATED AT 250 WORDS)