Vaccination success depends not only on supply and access, but on public willingness to vaccinate, which is shaped by complex psychological and sociocultural factors. This chapter synthesizes evidence from cross‑national surveys, longitudinal field studies, and contemporary behavioural science to examine the psychological and social drivers of vaccine demand. We outline how attitudes toward vaccines are shaped by trust, identity, ideology, and broader sociocultural contexts, and translate into real‑world behaviours. Predominant theoretical models are reviewed. Finally, we outline interventions that show promise, including consensus messaging and empathetic refutation, illustrating how effective vaccine communication must engage underlying motivations and bolster trust in order to support vaccine demand in an era of misinformation. Increasing vaccine uptake requires not only improved access, but also needs sustained, psychologically attuned, and empathetic engagement.