The analysis of medical texts, as well as of some locations of his biographies, points out Kant's opposition to any kind of smallpox prevention. Far from being original, his objections are a slavish repetition of Wagstaffe's anti-inoculation positions, refuted by Hume, De La Condamine and Verri. As for vaccination, he resorts the argumentations of nineteenth century's vaccinophobics spreading the idea of a "minotaur syndrome" risk, given by the contact of a human being and the vaccine pus. This belief was overcome by the wide diffusion of Jenner's ideas on prophylaxis. Kant's adherence to such antiscientific visions on the most important medical matter of his time raises a concrete question about the extended use of his moral philosophy in relationship to the contemporary bioethics.