Mandatory vaccination has been a highly disputed policy for tackling infectious diseases. Here I argue that a universal mandatory vaccination policy for the general public against the COVID-19 pandemic is ethically preferable when grounded in the concept of solidarity, which is defined by Barbara Prainsack and Alena Buyx as an enacted commitment to a relevant respect recognized by a group of individuals with equal moral status. This approach is complementary to utilitarian accounts and could better address other reasonable oppositions to mandatory vaccination. From a solidaristic account, the recognized relevant respect is to end the COVID-19 pandemic as soon as possible. This group of individuals would be willing to carry costs to assist each other in this respect, and a mandatory vaccination policy could be their institutionalized mutual assistance. The costs to be carried include both the financial costs of vaccination and the health costs stemming from potential adverse events and scientific uncertainties. The proposed social health insurance similarity test suggests the degree of coercion the mandatory vaccination policy could undertake within each state's specific legal and judicial context. (Am J Public Health. 2022;112(2):255-261. https://doi.org/10.2105/AJPH.2021.306578).