Vaccines have been crucial in reducing mortality and morbidity around the world, particularly in low- and middle-income countries. Furthermore, vaccinations have also resulted in a considerable amount of economic savings. However, there are a growing number of individuals who express a strong skepticism of vaccine safety and effectiveness. These “vaccine-hesitant” individuals choose to reject or delay vaccine administration. A number of strategies have been developed to address the various socioeconomic and cultural circumstances of each vaccine-hesitant individual. However, there is a need to clarify the various factors that promote vaccine acceptance, delay, and rejection. In this article, we discuss the factors that promote vaccine hesitancy from recent research, describe some of the interventions we know to be effective in reducing hesitancy, and develop an agenda for researchers and students interested in vaccine hesitancy research.