The carriage rates in both rAOM and control groupings are considerably less than we within Aboriginal children from the same age within this study. and 63.3% respectively of kids <5 years, and 34.6%, 22.4% and 27.2% of individuals 5 years. Of 43 pneumococcal serotypes determined, the most frequent were Snap23 19A, 16F and 6C in kids <5 years, and 15B, 34 and 22F in older people. 7vPCV serotypes accounted for 14.5% of all serotypeable isolates, 13vPCV for 32.4% and 23vPPV for 49.9%, with little variation across all age groups. Serotypes 1 and 12F were rarely identified, despite causing recent IPD outbreaks in WA. Complete penicillin resistance (MIC 2g/ml) was found in 1.6% of serotype 19A (5.2%), 19F (4.9%) and 16F (3.2%) isolates and reduced penicillin susceptibility (MIC 0.125g/ml) in 24.9% of isolates, particularly 19F (92.7%), 19A (41.3%), 16F (29.0%). Multi-resistance to cotrimoxazole, tetracycline and erythromycin was found in 83.0% of 23F isolates. Among non-serotypeable Pitavastatin calcium (Livalo) isolates 76.0% had reduced susceptibility and 4.0% showed complete resistance to penicillin. == Conclusions == Ten years after introduction of 7vPCV for Aboriginal Australian children, 7vPCV serotypes account for a small proportion of carried pneumococci. A large proportion of circulating serotypes are not covered by any currently licensed vaccine. == Introduction == Invasive pneumococcal disease (IPD), which includes pneumonia, meningitis, and septicaemia, causes an estimated 476,000 deaths in children < 5 years annually, the majority of which occur in the third world [1]. In Western Australia (WA) between 1997 and 2007, the overall IPD incidence rate was 47 cases per 100,000 population per year in Aboriginal people, 6.7 times higher than the IPD incidence in non-Aboriginal people [2]. Furthermore, Aboriginal children experience high rates of otitis media (OM), often caused byStreptococcus pneumoniae, with up to 21% of children in WA having a tympanic membrane perforation before the age of 2 years in remote areas [3]. OM and its complications can have profound effects on hearing and subsequently can impact on speech and language development and behaviour. Overcrowding and indoor smoking are common in the Aboriginal population and associated with increased risk of nasopharyngeal bacterial carriage which is a necessary precursor to IPD and OM [4]. In 2001 the seven-valent pneumococcal conjugate vaccine (7vPCV, Prevenar), covering serotypes 4, 6B, 9V, 14, 18C, 19F and 23F, was introduced for Aboriginal Australian children in a 2-4-6-month Pitavastatin calcium (Livalo) schedule, with a catch-up schedule for children < 2 years of age, and for children < 5 years of age with predisposing medical conditions. A booster of 23-valent pneumococcal polysaccharide vaccine (23vPPV, Pneumovax 23, covers 7vPCV serotypes and 1, 2, 3, 5, 7F, 8, 9N, 10A, 11A, 12F, 15B, 17F, 19A, 20, 22F and 23F) was offered at age 18 months to Aboriginal children. In 2005 the 7vPCV program was extended to include all Australian children. On 1 July 2011 13vPCV replaced 7vPCV (covering six additional serotypes; 1, 3, 5, 6A, 7F, 19A) in the immunization schedule and a fourth dose of 13vPCV replaced the 23vPPV booster in Pitavastatin calcium (Livalo) Aboriginal children. Since the introduction of 7vPCV, the incidence of IPD caused by vaccine serotypes has fallen but IPD due to non-7vPCV serotypes has increased, and almost doubled in WA Aboriginal adults aged 30-49 years [2]. Serotypes which have emerged since the introduction of 7vPCV in WA include 1, 12F and 19A [5]. Surveillance of IPD in WA is limited by the need to administer antibiotics in remote areas before a sample of blood for culture can be collected at a referral hospital, and by the low sensitivity of blood culture. In addition, the Aboriginal population in WA is relatively small (around 77,000), and while the incidence of IPD Pitavastatin calcium (Livalo) is high, small numbers of cases make it difficult to monitor trends effectively. Given these limitations, surveillance of nasopharyngeal pneumococcal carriage assists in identifying serotypes circulating in the population, helping to predict changes in serotypes causing IPD [6]. Carriage studies facilitate Pitavastatin calcium (Livalo) monitoring the impact of PCV programs, which alter carriage and associated herd immunity. Studying pneumococcal carriage also allows antimicrobial susceptibility patterns to be monitored which can guide management of common non-invasive infections such as OM and pneumonia. While few reports exist on pneumococcal carriage in Aboriginal Australians prior to the introduction of 7vPCV, carriage studies in the Northern Territory indicate that 7vPCV reduced carriage of 7vPCV serotypes, similar to trends observed elsewhere [79]. Since 2008, we have studied nasopharyngeal carriage of bacterial pathogens in the Aboriginal population in WA. Our aim is to monitor nasopharyngeal carriage of pneumococcal serotypes, as well as the prevalence of other commonly carried pathogens,.