Risk factors and comorbidities for invasive pneumococcal disease in Western Australian Aboriginal and non-Aboriginal people

Australian Aboriginal people have among the highest rates of invasive pneumococcal disease (IPD) worldwide. We investigated clinical diagnosis, risk factors, comorbidities and vaccine coverage in Aboriginal and non-Aboriginal IPD cases. Using enhanced surveillance, we identified IPD cases in Western Australia, Australia, between 1997 and 2007. We calculated the proportion with risk factors and comorbidities in children (<5 years) and adults (=15 years), as well as adults living in metropolitan and non-metropolitan regions. We then calculated the proportion of cases eligible for vaccination who were vaccinated before contracting IPD. Of the 1,792 IPD cases that were reported, 355 (20%) were Aboriginal and 1,155 (65%) were adults. Pneumonia was the most common diagnosis (61% of non-Aboriginal and 49% of Aboriginal adult IPD cases in 2001–2007). Congenital abnormality was the most frequent comorbidity in non-Aboriginal children (11%). In Aboriginal children, preterm delivery was most common (14%). Ninety-one percent of non-Aboriginal and 96% of Aboriginal adults had one or more risk factors or comorbidities. In non-Aboriginal adults, cardiovascular disease (34%) was the predominant comorbidity whilst excessive alcohol use (66%) was the most commonly reported risk factor in Aboriginal adults. In adults, comorbidities were more frequently reported among those in metropolitan regions than those in non-metropolitan regions. Vaccination status was unknown for 637 of 1,082 cases post-July 2001. Forty-one percent of non-Aboriginal and 60% of Aboriginal children were eligible for vaccination but were not vaccinated. Among adults with risk factors who were eligible for vaccination and with known vaccination status, 75% Aboriginal and 94% non-Aboriginal were not vaccinated. An all-of-life immunisation register is needed to evaluate vaccine coverage and effectiveness in preventing IPD in adults.