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Impact of immunization on Haemophilus influenzae type b disease
1Wyeth-Lederle Vaccines and Pediatrics, West Henrietta, New York, U.S.A.
Insights
Effective Haemophilus influenzae type b (Hib) conjugate vaccines have significantly reduced invasive Hib disease in young children. These vaccines also decrease Hib transmission and offer economic benefits.
Area of Science:
- Pediatrics
- Epidemiology
- Immunology
Background:
- Haemophilus influenzae type b (Hib) was a leading cause of bacterial meningitis and epiglottitis in children before vaccine introduction.
- Invasive Hib disease posed a significant public health burden globally.
Purpose of the Study:
- To evaluate the impact of Haemophilus influenzae type b (Hib) conjugate vaccines on invasive disease incidence and transmission.
- To assess changes in causative agents of meningitis and epiglottitis following widespread Hib vaccination.
Main Methods:
- Analysis of epidemiological surveillance data before and after Hib vaccine introduction.
- Monitoring of invasive Hib disease incidence, epiglottitis, and pharyngeal carriage rates.
- Comparison of disease trends in vaccinated versus unvaccinated age groups.
Main Results:
- A rapid decline in invasive Hib disease incidence was observed temporally associated with vaccine introduction.
- Hib conjugate vaccine use reduced disease in children under 5 years, with decreased pharyngeal carriage rates.
- Other bacterial pathogens are now primary causes of infant meningitis and epiglottitis, with unchanged incidence.
Conclusions:
- Hib conjugate vaccines are highly effective in preventing invasive Hib disease and reducing transmission.
- Vaccination has shifted the burden of pediatric meningitis and epiglottitis to other pathogens.
- Hib vaccination programs provide substantial public health and economic benefits.
Abstract:
Epidemiological surveillance programs have shown that before the introduction of effective vaccines, Haemophilus influenzae type b (Hib) was the primary pathogen associated with bacterial meningitis in children. Vaccines composed of the bacterium's polysaccharide conjugated onto protein carriers began to be introduced into routine health care practices for infants as early as 1989 in some European countries. Continued introduction in industrialized nations, including the United States in late 1990, has resulted in the rapid decline in the incidence of reported invasive Hib disease. Follow-up surveillance studies show that (a) the decline in the incidence of Hib disease is temporally related to the introduction of effective vaccines, (b) the decline in Hib epiglottitis preceded the decline in meningitis in the United States, (c) the incidence of disease declined in children under the age of 5 years but remained constant in older children and adults, (d) other bacterial pathogens are now the primary causative agents of infant meningitis and epiglottitis even though the incidence of disease caused by these other pathogens has not changed, and (e) the pharyngeal carriage rate of Hib in children has declined without any evidence of an increase in the carriage of non-type b strains or other pathogens. The introduction of effective conjugate vaccines appears to protect at-risk children from invasive Hib disease as well as reduce the opportunities for interpersonal transmission of this bacterium. In addition, Hib conjugate vaccine utilization has benefited society through economic savings.