Our surveys and experiments consistently suggested that making vaccination a requirement for work, attending school, or travelling is likely to be successful in promoting vaccination, more so than either giving people freedom to choose or reminding them of the freedom the vaccine might confer. Also, we found no evidence that requirements elicited reactance in a way that undermined the likely efficacy of a vaccine mandate. Rather, the behavioral intentions of participants who scored higher in trait psychological reactance were either more positively influenced by the requirement (see Study 3) or as influenced as their lower reactance counterparts (see Study 4). Study 4 also showed that participants who were higher in psychological reactance felt less obligated to vaccinate when the vaccine was required than when it was not. This result is intriguing and suggests that psychological reactance might lead people to feel less morally obligated to follow a mandate but still be motivated to vaccinate. All in all, our results suggest that fears about a mandate backfiring may be unfounded and support vaccine mandates as a strategy for achieving herd immunity for COVID-19 in the United States.