In mid-August 2021, the Centers for Disease Control and Prevention (C.D.C.) issued a recommendation for both vaccinated and unvaccinated Americans to begin wearing masks in public again, particularly in places experiencing outbreaks of COVID-19, driven by the Delta variant. Further compounding this concern is the lower propensity of unvaccinated individuals to wear masks. For example, a report from July 2021 found that unvaccinated Americans, on average, tended to wear masks less than vaccinated Americans by a margin of 25 percentage points.Given the link between mask-wearing and vaccination, discussions of behaviors relating to COVID-19 often lump people into two categories: those who behave in ways that prevent the spread of COVID-19 and those who do not. However, doing so misses the complexity of who engages or doesn’t engage in behaviors that stem the spread of COVID-19, or why they do so. Vaccination and mask-wearing are two different means to the same end: preventing infection. They are, in part, driven by the same factor, concern over infection. But they are also partial substitutes, aimed at the same target, preventing infection. In our data, we find that 30% of the population is either vaccinated and unmasked; or unvaccinated and masked. Indeed, most unvaccinated individuals report wearing masks. Understanding this complexity is significant in getting people vaccinated, and in getting people to wear masks - particularly those who are unvaccinated. In this report, we divide Americans into four categories and investigate the tendencies of each group: (1) those who report wearing masks and who are unvaccinated (“the masked unvaccinated”), (2) those who report wearing masks and who are vaccinated (“the masked vaccinated”), (3) those who report not wearing masks and who are unvaccinated (“the unmasked unvaccinated”), and (4) those who report not wearing masks and who are vaccinated (“the unmasked vaccinated”).