Introduction
DISEASE
COVID-19 vaccination has been critical for controlling the COVID-19 pandemic by protecting vulnerable individuals from severe disease, safeguarding health systems and helping return society to normal functioning [Suboptimal uptake of COVID-19 booster doses has occurred globally. In Australia, completion of a primary course of COVID-19 vaccine for individuals ≥16 years is >96%, but booster dose (third dose) coverage has stalled at just over 70% [While many factors can contribute to low vaccine uptake, including both access and acceptance barriers, low motivation may continue to act as a barrier to uptake if not addressed [Considering these findings, emphasising motivational factors in persuasive messaging could potentially be a successful strategy to support higher intention to receive a COVID-19 vaccine. There is evidence that persuasive messages can support higher intentions towards vaccination in general [Given the current state of evidence, it remains unclear what types of messages have the greatest effect on intention to receive a booster dose of COVID-19 vaccine. This is especially the case in populations that have experienced relatively low risk of encountering COVID-19, combined with restrictive public health measures. These were the conditions experienced in Australia at the time of this experiment, where COVID-19 case numbers were relatively low during the first two years of the pandemic, while public health restrictions, such as border closures and lockdowns, were applied liberally due to the country’s pursuit of a COVID-19 elimination strategy [