"Vaccines, Belief, and Conversation: Trust Dynamics in Health Messaging Games

In the age of global health crises, especially during and after the COVID-19 pandemic, the uptake of vaccines has been shaped not only by clinical evidence but also by the quality and nature of communication strategies. This paper explores how strategic communication—particularly in the forms of cheap talk and small talk—can influence public beliefs, intentions, and decisions about vaccination. Using a game-theoretic framework, we model interactions between health authorities (or advertisers) and individuals, analysing how different signalling strategies affect public welfare and vaccine coverage. Cheap talk, traditionally viewed as costless and non-credible, is reconsidered in the context of repeated interactions and belief dynamics. Small talk, while socially trivial on the surface, is shown to generate trust and reduce informational asymmetries in health contexts. Through a payoff matrix, we establish that small talk, when perceived as genuine and empathetic, leads to Nash equilibria that favour vaccination and societal welfare. The study further explores real-world implications, including government vaccination campaigns, influencer endorsements, and communication via social media. Ultimately, we propose a belief-driven strategic model that positions small and cheap talk as vital tools in addressing vaccine hesitancy and misinformation. The findings offer insights for public health policy, advertising strategies, and trust-building in uncertain health environments.