Data on vaccination coverage were provided by Medicare Australia from the Australian Childhood Immunisation Register (ACIR). Data on adults from the 2004–05 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS), and 2004–05 and 2001 National Health Surveys (NHS) were provided by the National Centre for Aboriginal and Torres Strait Islander Statistics of the Australian Bureau of Statistics.
The ACIR is administered by Medicare Australia for the Australian Government Department of Health and Ageing, and records the vaccination service details of children aged less than 7 years from data supplied by vaccination service providers. Vaccination coverage estimates derived from ACIR data have been reported in Communicable Diseases Intelligence since early 1998. The methodology for calculating cohort-based vaccination coverage from the ACIR was published with the first coverage estimates in 1998.15 Using this method, a cohort of children is defined by date of birth in three-month groups, the first cohort being born between 1 January 1996 and 31 March 1996. The vaccination status of each cohort is assessed at the three key milestones of 12 months, 24 months and 72 months of age. Coverage is measured several months after the due date for completion of each milestone, to allow for delayed notification to the ACIR. To minimise duplicate records, the cohort includes only children enrolled with Medicare (approximately 99% of children). When multiple doses are required, it is assumed that notification of receipt of a later vaccine dose implies receipt of earlier doses (‘third-dose assumption’).15,16
The reporting of Indigenous status has improved markedly in recent years so that, by 2005, 95% of the ABS-estimated cohort of Aboriginal and Torres Strait Islander babies were recorded as such on the ACIR, with a minimum of 75% across jurisdictions.17 Variations in Indigenous status reporting rates were also shown to have little impact on coverage estimates,17 with the estimates produced in 2003, when the ACIR included only 50% of the ABS-estimated cohort, comparable with the estimates from a household survey in Queensland.18 Coverage for the 72 month milestone is presented for the first time in this report, as the ACIR now includes approximately 80% of the ABS-estimated Aboriginal and Torres Strait Islander cohort for this age group.
The methodology for the survey and for calculating vaccination coverage estimates in the 2004–05 National Aboriginal and Torres Strait Islander Health Survey have been published.19 The 2004–05 NATSIHS was conducted in private dwellings selected throughout Australia, including remote areas. Information was obtained from both adults and children (0–17 years) in the selected households. The NATSIHS sample was combined with Aboriginal and Torres Strait Islander Australians enumerated as part of the 2004–05 NHS to provide a total sample of 10,439 Indigenous persons. It should be noted that Aboriginal and Torres Strait Islander children from remote areas, except for those aged 15–17 years, were not surveyed regarding vaccination, and Indigenous adults from remote areas were only asked a limited set of survey questions regarding vaccination. Remote areas are defined as those living in areas of remoteness classified as ‘Remote Australia’ or ‘Very Remote Australia’ according to the Australian Standard Geographic Classification used by the Australian Bureau of Statistics.
Vaccination status information was collected by face-to-face interviews. Adult respondents (aged 18 years or more) from both non-remote and remote areas were asked whether they had been vaccinated against pneumococcal disease in the last five years and against influenza in the last 12 months. The same questions were asked in the National Health Survey 2001.
Compared with the Indigenous supplementary component of the 2001 NHS, new vaccination information that was collected in the 2004–05 NATSIHS included influenza and pneumococcal vaccination status in Indigenous people aged 15–49 years in both non-remote and remote areas (in addition to adults aged 50 years or more).
Data collected through the NATSIHS on the prevalence of risk factors for which the influenza and pneumococcal vaccine were recommended in Aboriginal and Torres Strait Islander people aged 15–49 years20 were also obtained. Appendix C lists the conditions that were selected as representing those risk factors.
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