The COVID-19 pandemic tested public health communication like never before. While providing information is crucial, does it always translate into action? In this episode of “Accelerating Development,” we delve into a groundbreaking World Bank meta-analysis on COVID-19 vaccination intentions. Drawing on insights from the 2015 World Development Report "Mind, Society, and Behavior," we examine how behaviorally informed messages – considering how people think socially and use mental models – significantly impacted public responses. From the power of trusted messengers to the nuances of message framing and the complexities of heterogeneity across contexts, we explore the methodological innovations and critical research frontiers this study illuminates for accelerating development through a deeper understanding of human behavior.