Awareness, Risk Perception and Prior Uptake as Determinants of Intention to Receive an Annual COVID-19 Booster Among Australian Adults: A Cross-Sectional Survey

Background: Two-dose COVID-19 vaccine coverage exceeded 95% of Australian adults, yet only about one in three received a booster during 2023, according to Australian Government vaccination coverage data. The survey period marked Australia’s transition from emergency pandemic response to recurring COVID-19 vaccination. This study aimed to identify factors associated with Australian adults’ intention to receive annual COVID-19 boosters. Methods: We surveyed 2582 Australian residents aged ≥18 years between 9 and 25 January 2023 via a global market research panel. The outcome was intention to receive an annual booster (yes versus no or unsure). Predictors were identified by multivariable logistic regression with backward stepwise selection and bootstrap validation; free-text explanations underwent inductive content analysis. Results: Overall, 62.3% of respondents intended to receive an annual COVID-19 booster if needed, 15.7% were unsure, and 22.0% did not intend to do so. Only 9.4% knew that a newly available bivalent vaccine existed. The strongest independent predictors were ≥3 prior doses [adjusted odds ratio (aOR) 4.26, 95% CI 3.31–5.49], perceiving vaccines as effective (aOR 4.22, 3.44–5.18) and knowing the bivalent vaccine was available (aOR 4.06, 2.47–6.68). Believing the pandemic was not over, age ≥ 65 years, perceiving COVID-19 as worse than influenza and having ≥1 comorbidity were also independently associated with intention. Among non-intenders, the most commonly reported reasons were perceived vaccine ineffectiveness (46.4%) and the belief that boosters were unnecessary (34.6%), while safety concerns were less frequently reported. Conclusions: Intention to receive an annual booster was shaped less by safety fears than by beliefs about effectiveness and awareness of availability. Awareness that a bivalent vaccine existed was among the strongest correlates of intention, yet fewer than one in ten adults had it, making awareness a modifiable system-level target.