This three-phase mixed-methods research project starts with gathering and analyzing evidence of trust-building measures and practices from existing research and programs worldwide. Additionally, the team will identify survey data that informs measuring trust in vaccines. These findings will be presented to the expert panel of advisors for their review of validity and utility in the U.S. context. The second phase consists of targeted primary research of the determinants of trust in vaccines. The team will then host a national survey to identify 30 interviewees from vaccine-hesitant populations and communities of color underserved by the present health care system. An oversample of interviewees who identify as Black and Latino will aim to ensure adequate representation of populations disparately affected by COVID-19. In the third phase, the team will organize a formal expert panel to review the research findings to refine recommendations and support the development of new vaccine communication strategies, messages, and tools, as well as support dissemination of a report and recommendations for implementation.