Invasive Pneumococcal Disease in the Northern Territory of Australia, 1994-1998

Objective: To examine the epidemiology of invasive pneumococcal disease (IPD) in the Northern Territory of Australia as a basis for optimising vaccination and healthcare provision.

Design: Prospective laboratory surveillance, with information collected from hospital and clinic records.

Setting: Northern Territory (NT) and rural communities in north-west South Australia served by an NT hospital, 1994-1998 (NT population is 27% Indigenous).

Main Outcome Measures: IPD incidence and mortality, risk factors, clinical presentation and disease-causing serotypes in Indigenous and non-Indigenous people.

Results: 425 cases of IPD were detected, with 77% in Indigenous people. IPD incidence was highest in Indigenous children aged < 2 years (1534 per 100,000 in central Australia), but about 100 per 100,000 in non-Indigenous children < 2 years and all Indigenous age groups aged > or = 15 years. Mean ages of those with disease were 39 years in Indigenous people and 48 years in non-Indigenous people (P = 0.006) and, of those who died, 41 and 53 years, respectively (P = 0.04). IPD risk factors were present in 72% of Indigenous and 55% of non-Indigenous patients aged > or = 2 years. Serotype results for 363 isolates showed that the 23-valent vaccine covered 68% and 85% of isolates from Indigenous and non-Indigenous people aged > or = 2 years, respectively, while the proposed seven-, nine- and 11-valent conjugate vaccines covered 58%, 66% and 67% of isolates, respectively, from Indigenous children aged < 2 years and 72% each of those from non-Indigenous children. Case-fatality rates were 10% in both Indigenous and non-Indigenous people.

Conclusion: These data support the recent change in NT vaccination policy which extended funding for the 23-valent vaccine to all Indigenous people aged > or = 15 years and all Indigenous children in central Australia aged 2-5 years. The high rates of IPD in both Indigenous and non-Indigenous children mandate action to make conjugate vaccine available as soon as possible.