Invasive pneumococcal disease in the Australian Capital Territory and Queanbeyan region: do high infant rates reflect more disease or better detection?

Abstract

To describe the epidemiology of invasive pneumococcal disease in the Australian Capital Territory (ACT) and Queanbeyan region prior to the introduction of conjugate pneumococcal vaccines. Residents with sterile site isolates of Streptococcus pneumoniae from 1998 to 2000 were identified from a prospective bacteraemia surveillance project involving all ACT public hospitals, supplemented by retrospective laboratory-based detection of other sterile site isolates. Incidence of invasive pneumococcal disease was 15.2 cases per 105 per year, and 193.4 per 105 per year in infants under 2 years. Primary bacteraemia was significantly more common in infants and young children than in older subjects. Reduced penicillin susceptibility was observed in 9.6% of isolates, and no high-level penicillin resistance was observed. Infants in the ACT and Queanbeyan have a higher invasive pneumococcal disease incidence than similar populations worldwide. Better detection is the most likely explanation. This population would be ideal for studies of the 'real life' effectiveness of infant conjugate vaccination.