Decreases in invasive Haemophilus influenzae diseases in US Army children, 1984 through 1991

Objective. —To document trends in the incidence of invasiveHaemophilus influenzaediseases in young children of US Army active duty soldiers following the publication ofH influenzaetype b immunization recommendations for young children between 1985 and 1990. Design. —A population-based surveillance of hospital discharge diagnoses forH influenzaeinvasive diseases. Setting. —Military and civilian medical treatment facilities around the world. Patients. —There was a mean population of nearly 200 000 US Army health care beneficiaries younger than 5 years of age each year of the study. Outcome Measures. —Annual total and age-specific incidences of the six most commonH influenzaeinvasive diseases in this population (meningitis, epiglottitis, septicemia, pneumonia, cellulitis, and septic arthritis). Results. —The annual number of cases ofH influenzaeinvasive diseases decreased from a high of 188 in 1986 to 43 in 1991. The incidence in the age group at highest risk forH influenzaedisease, those 6 to 11 months of age, decreased from 355 per 100 000 children in 1986 to 116 per 100 000 in 1991 (P<.0001 χ2for trend). The incidence forH influenzaemeningitis declined from 59 per 100 000 children in 1986 to 6 per 100 000 in 1991 (P<.0001, χ2for trend). Conclusions. —The decrease inH influenzaeinvasive diseases closely follows the dates ofH influenzaetype b vaccine licensure for use in progressively younger age groups. Some age groups, however, experienced a decline in disease rates even before becoming eligible for vaccination. (JAMA. 1993;269:227-231)