For a public health campaign to succeed, the public sector is expected to debunk the misinformation transparently and vividly and guide the citizens. The present study focuses on COVID-19 vaccine misinformation in Hong Kong, a non-Western society with a developed economy and sufficient vaccine supply but high vaccine hesitancy. Inspired by the Health Belief Model (HBM) and research on source transparency and the use of visuals in the debunking, the present study examines the COVID-19 vaccine misinformation debunking messages published by the official social media and online channels of the public sector of Hong Kong (n = 126) over 18 months (1 November 2020 to 20 April 2022) during the COVID-19 vaccination campaign. Results showed that the most frequently occurring misinformation themes were misleading claims about the risks and side effects of vaccination, followed by (non-)effectiveness of the vaccines and the (un)-necessity of vaccination. Among the HBM constructs, barriers and benefits of vaccination were mentioned the most, while self-efficacy was the least addressed. Compared with the early stage of the vaccination campaign, an increasing number of posts contained susceptibility, severity or cues to action. Most debunking statements did not disclose any external sources. The public sector actively used illustrations, with affective illustrations outnumbering cognitive ones. Suggestions for improving the quality of misinformation debunking during public health campaigns are discussed.

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