The retreat of Hemophilus influenzae type B invasive disease: analysis of an immunization program and implications for OTO-HNS.

Hemophilus influenzae type b (Hib) is the most common cause of bacterial meningitis among children under 5 years old. Hib is also responsible for other invasive diseases including epiglottitis, cellulitis, sepsis, pneumonia, and osteomyelitis. A child's cumulative risk of systemic Hib disease during the first 5 years of life is approximately 1 in 200. A polysaccharide Hib vaccine was first marketed in 1985, and newer, more effective conjugated vaccines have been licensed since 1987. Immunization schedules have included increasingly younger children. No studies have been published that analyze the effects of a vigorous immunization program on a sample population representative of the United States at large. Records of pediatric patients ages 5 years and younger who were treated for Hib meningitis or epiglottitis (N = 373) at all U.S. Army medical facilities between 1986 and 1991 were reviewed. The combined incidence of these diseases declined by more than 86% in the study group during this period. The largest decrease occurred in infants less than 1 year old, before vaccines were licensed for use in this group. Meanwhile, the number of cases of bacterial meningitis due to other organisms in this cohort remained unchanged. Economic modeling validates the cost-effectiveness of vaccination. The impact of these preliminary trends on health care systems and otolaryngology-head and neck surgery will be significant. Almost two thirds of Hib disease has involved infants under 15 months old, for whom a conjugated vaccine has been available only since October 1990. The change in disease frequency will have substantial bearing on training programs, because management of neurologic sequelae and the emergent airway require the expertise of otolaryngologists. In the face of medical onslaught, Hib invasive disease is in retreat.