This dissertation examines the collaboration between public health officials, government administrators, and Roman Catholic clergy in propagating smallpox vaccination as a case study for modern state building in post-revolutionary France. The interdisciplinary nature of my research, which considers the dialogue between government, medical, and religious sources, challenges the medical-historical community to rethink the role of religious institutions in the promotion of public health measures in the modern era.The most important concern that shaped vaccination debates was the degree the Church should do the work of the state and the significance of that collaboration for Catholics in an increasingly secular France. At a time when boundaries between secular and religious authority were questioned and refashioned, religious authorities served an important role as intermediaries between Parisian health officials and far-flung parishes and villages. This interaction between religion and vaccination demonstrates how religious institutions in particular mediated between the demands of the post-revolutionary state and the aspirations of a people understood equally as laity and citizens. At a time when boundaries between secular and religious authority were questioned and refashioned, the relationship between religion, medicine, and government was, on the whole, collaborative rather than obstructive.