Invasive Haemophilus influenzae infection in the Australian Capital Territory region.

Abstract

To investigate the pattern of invasive Haemophilus influenzae disease in the Australian Capital Territory (ACT) region with a view to assessing the possible benefits of vaccination in this community. The microbiology department of Royal Canberra Hospital processes all specimens from the three public hospitals in the ACT. Together these hospitals provide all paediatric medical and approximately 80% of adult inpatient beds available in the ACT. We identified all laboratory isolates of H. influenzae obtained from normally sterile sites from 1984 to 1990, and reviewed the clinical records of these patients. Also included in this analysis were all cases of acute epiglottitis identified in hospital discharge summaries, intensive care and coroners' records. Epidemiological, clinical and microbiological data were gathered and assessed. We identified 138 cases of infection. Forty per cent (36 of 66 cases of meningitis, 5 of 44 cases of epiglottitis, 10 of 12 cases of cellulitis) occurred in children aged less than 18 months. Meningitis (48%), epiglottitis (32%), cellulitis (9%) and primary bacteraemia (4%) were the most common syndromes seen. The annual incidence of invasive H. influenzae disease in Canberra was 63.2 per 100,000 children aged under five years. Approximately 1 in 225 children under five years of age and resident in Canberra developed invasive H. influenzae disease. Ninety-eight per cent of isolates serotyped were type b. A vaccination program effective in preventing H. influenzae type b infection, completed in infants before 6 months of age, could prevent upwards of 80% of invasive H. influenzae disease in our population. Such a program should be cost effective although precise assessment is hampered by the lack of accurate data on the acceptance rate, costs and efficacy of the current childhood vaccination schedule in our region.