"As soon as it's trying to be persuasive, my skepticism kicks in": A qualitative study to co-design vaccine communication strategies with vaccine hesitant adults in Canada.

Vaccine hesitancy continues to impede vaccine uptake in Canada. Few interventions directly engage hesitant adults in co-designing communication materials. This study aimed to co-develop and evaluate digital vaccine communication messages with hesitant adults in Canada to improve message relevance and trustworthiness. Using a qualitatively driven design with an exploratory user-test survey, we conducted two rounds of 4 focus groups (n = 31) with self-identified vaccine hesitant adults across Canada to co-design and refine three digital interventions (a video, an infographic, and a social media graphic). Insights from the focus groups informed a brief survey that assessed acceptability, perceived effectiveness, relevance and perceived influence on subsequent behaviors. Participants represented Fence-sitters and Cautious Acceptors across ages, genders, and regions in Canada. Focus groups generated three overarching themes reflecting adult health communication preferences: (1) confidence fostered through credible, consistent and transparent sources, (2) readable, relatable and visually engaging messaging, and (3) positive, encouraging messaging that fosters emotional connection rather than fear-driven persuasion. These principles shaped the three final co-designed messages. Survey responses suggested high acceptability of the infographic (90%) and video (90%). Across formats, expert-delivered content, concise visuals, and transparent data were the most persuasive features. Mixed reactions to fear-based elements informed a deliberate choice to avoid using coercive or fear-based framing, resulting in a more encouraging final tone. This study moves beyond identifying communication gaps by presenting concrete, co-created strategies for building trust with vaccine hesitant adults. Future research should test these strategies at scale to assess their impact on vaccine confidence and uptake.