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Epidemiology and prospects for prevention of disease due to Haemophilus influenzae in developing countries
R S Munson1, M H Kabeer, A A Lenoir
1Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.
Abstract:
Haemophilus influenzae is an important cause of meningitis and severe cases of lower respiratory infection (LRI) in children in developing countries. In children with meningitis, H. influenzae type b organisms are the most frequently encountered serotype, but in some countries type a strains are also implicated. In children with LRI, type b organisms are also important, but the proportion of organisms with other serotypes and non-typable strains is greater than that associated with cases of meningitis. In developing countries, nearly all cases of H. influenzae meningitis and a substantial fraction of cases of LRI occur in children younger than one year of age. This age distribution is younger than that seen in the continental United States, where more than one-half of the cases of invasive H. influenzae disease are in children older than one year of age. New type b polysaccharide-protein conjugate vaccines are immunogenic in infants as young as two months of age and offer the promise of preventing H. influenzae type b disease in infants younger than one year of age. However, for developing countries, more complete data defining the populations at risk, the immunogenicity of candidate vaccines in children in different geographic regions, and the serotypes of the infecting organisms will be needed before successful cost-effective vaccination strategies can be devised and implemented.
Insights
Haemophilus influenzae causes severe childhood meningitis and respiratory infections, particularly in infants under one year old in developing nations. New conjugate vaccines show promise, but more data is needed to tailor effective vaccination strategies for these regions.
Area of Science:
- Pediatrics
- Infectious Diseases
- Vaccinology
Background:
- Haemophilus influenzae is a significant pathogen causing meningitis and lower respiratory infections (LRI) in children globally.
- In developing countries, H. influenzae type b is a primary cause of meningitis, while type a and non-typable strains are also implicated in LRI.
- Invasive H. influenzae disease predominantly affects infants younger than one year in developing nations, contrasting with older children in developed countries.
Purpose of the Study:
- To highlight the epidemiological differences in H. influenzae disease burden and age distribution between developing countries and the United States.
- To discuss the potential of new Haemophilus influenzae type b polysaccharide-protein conjugate vaccines for infant immunization.
- To identify data gaps crucial for developing effective and cost-efficient vaccination strategies in developing countries.
Main Methods:
- Review of existing epidemiological data on Haemophilus influenzae infections in children.
- Analysis of serotype distribution in meningitis versus LRI cases.
- Comparison of age-specific incidence rates between developing countries and the continental United States.
- Evaluation of the immunogenicity data for new conjugate vaccines in infants.
Main Results:
- Haemophilus influenzae type b is the most common serotype in meningitis cases among children in developing countries.
- A higher proportion of non-type b and non-typable strains are associated with LRI compared to meningitis.
- The majority of invasive H. influenzae cases in developing countries occur in infants under one year old.
- New conjugate vaccines are immunogenic in infants as young as two months.
Conclusions:
- Haemophilus influenzae type b conjugate vaccines offer a promising approach to prevent invasive disease in young infants.
- Further research is essential to define at-risk populations, assess vaccine immunogenicity across diverse regions, and identify prevalent serotypes.
- Comprehensive data is required to implement successful and cost-effective vaccination programs in developing countries.