As a society, how do we address the "wicked hard problem" of vaccine acceptance? How can public health institutions reach those who are hesitant when even robust fact-based campaigns don't seem to work? Infectious diseases are one of the long-standing challenges for humanity; historical plagues and flare ups of disease have transformed societies, redrawn boundaries across the globe and instigated mass migrations. Successive civilizations have grappled with attempts to control contagion and tried to protect their populations. With the advent of vaccines in the late 1700's it seemed humanity had finally found the way out of this potentially existential threat. But despite humans' deeply embedded fear of infectious disease, issues of vaccine acceptance arose from the start. Through decades of public health campaigns in multiple countries, a persistent thread can be seen of reluctance to adopt vaccines, despite extensive educational campaigns or even coercive tactics to get populations fully vaccinated. Prerna Singh asks how do we go beyond the usual behavior modeling to find out what actually works for these critical public health campaigns? Can we uncover the keys to human motivation to get people to act for their own protection and for the greater good? This Long Now Talk is presented in partnership with the Center for Advanced Study in the Behavioral Sciences (CASBS) at Stanford University. CASBS brings together deep thinkers from diverse disciplines and communities to advance understanding of the full range of human beliefs, behaviors, interactions, and institutions. A leading incubator of human-centered knowledge, CASBS facilitates collaborations across academia, policy, industry, civil society, and government to collectively design a better future.