Abstract: To close existing research gap and combat vaccine hesitancy among young adults, we conduct this study to integrate psychological reactance theory to better understand the effectiveness of three emerging yet understudied emotional appeals (i.e., guilt, shame, and pride) in health risk context. The current research has two goals: (1) to examine how different emotional appeals (guilt vs. shame vs. pride) and user-generated comments toward COVID-19 vaccine messages independently or interactively affect psychological reactance and (2) to understand the mediating role of psychological reactance between emotional appeals and user-generated comments and desired behavioral outcomes. An experimental study with 3 (guilt vs. shame vs. pride) by 2 (positive-valenced comments vs. negative-valenced comments) between-subjects factorial design will be conducted with college students (aged 18-24) at a large public university in the United States. Our findings strengthen the theoretical foundation on how health risk messages with user-generated comments interactively can predict undesired health outcomes. Our study also helps health organizations design more effective messages targeting at young adults by lowering psychological reactance and enhancing persuasive power in motivating COVID-19 vaccination.