Objective Medicine is a scarce resource as well as a public good that benefits others by bettering patients’ health. COVID- 19 vaccines, which have been in shortage, are 1) a scarce resource and 2) a public good with the positive externality of building herd immunity. These features are expected to drive citizens’ attitudes in opposite directions: towards exclusion and towards inclusion, respectively. Due to scarcity, citizens may behave in an exclusionist manner; however, the presence of the positive externality might mitigate exclusionist attitudes. Setting and design We recruited 15,000 Japanese adults and asked them to rank, in the context of a COVID-19 vaccine shortage, the deservingness of hypothetical vaccine recipients who differ according to: 1) citizenship status, 2) visa type and duration of stay (if foreign), 3) occupation, 4) age, 5) whether they live with a child 5 years old or younger, and 6) whether they live with an elderly individual aged 65 or over. Citizenship options were Japanese, Chinese, Taiwanese, South Korean, American, or European. The occupations were healthcare, education, other employed, self-employed, or not employed. The 6 attributes were randomly combined, and respondents were shown 3 hypothetical vaccine recipients, one of whom was Japanese, with the others being foreigners. Treatments First, we created hypothetical vaccine recipients through a fully randomized conjoint design. Second, we randomly presented two scenarios for vaccination payment: 1) billed at cost or 2) fully subsidized by the government. Results 1) Whether the vaccines were billed at cost or fully subsidized did not affect the rankings of deservingness. 2) Japanese citizenship was prioritized over the other attributes. 3) The penalty for being a foreigner was higher for individuals from nations with which Japan has geopolitical tensions. 4) Working in health or education reduced the penalty on foreigners, indicating that the positive externality related to occupation amplifies the positive externality associated with vaccination and mitigates exclusionist attitudes regarding the allocation of scarce resources. 5) Women are less exclusionistic and valued the positive externalities from occupation more than men did. Conclusions On average, Japanese citizens prioritize other Japanese citizens. However, the positive externalities associated with occupation, which amplify the positive externality from vaccination, substantially allays the foreigner penalty.