Influenza vaccination coverage in a population-based cohort of Australian-born Aboriginal and non-Indigenous older adults

Background: There is limited information on vaccination coverage and characteristics associated with vaccine uptake in Aboriginal and/or Torres Strait Islander adults. We aimed to provide more current estimates of influenza vaccination coverage in Aboriginal adults. Methods: Self-reported vaccination status (n=559 Aboriginal and/or Torres Strait Islander participants, n=80,655 non-Indigenous participants) from the 45 and Up Study, a large cohort of adults aged 45 years or older, was used to compare influenza vaccination coverage in Aboriginal and/or Torres Strait Islander adults with coverage in non-Indigenous adults. Results: Of Aboriginal and non-Indigenous respondents aged 49 to <65 years, age-standardised influenza coverage was respectively 45.2% (95% CI 39.5–50.9%) and 38.5%, (37.9–39.0%), p-value for heterogeneity=0.02. Coverage for Aboriginal and non-Indigenous respondents aged ≥65 years was respectively 67.3% (59.9–74.7%) and 72.6% (72.2–73.0%), p-heterogeneity=0.16. Among Aboriginal adults, coverage was higher in obese than in healthy weight participants (adjusted odds ratio (aOR)=2.38, 95%CI 1.44–3.94); in those aged <65 years with a medical risk factor than in those without medical risk factors (aOR=2.13, 1.37–3.30); and in those who rated their health as fair/poor compared to those who rated it excellent (aOR=2.57, 1.26–5.20). Similar associations were found among non-Indigenous adults. Conclusions: In this sample of adults ≥65 years, self-reported influenza vaccine coverage was not significantly different between Aboriginal and non-Indigenous adults whereas in those <65 years, coverage was higher among Aboriginal adults. Overall, coverage in the whole cohort was suboptimal. If these findings are replicated in other samples and in the Australian Immunisation Register, it suggests that measures to improve uptake, such as communication about the importance of influenza vaccine and more effective reminder systems, are needed among adults.