Antifertility vaccination is a proposed method of contraception that induces infertility through an immunological response to specific reproductive targets. The following essay analyzes several peer-reviewed articles to identify these potential targets and then determines the bioethical implications of vac­cine use through the lens of Thomistic personalism. Vaccines that intentionally utilize a contraceptive action violate the principles of totality, integrity, and inseparability; while vaccines that intentionally utilize a contragestive action additionally violate the principles of inviolability of human life and non-maleficence. An (...) exception may exist in cases where application is directed at the treatment of specific pathologies. These cases may be tolerated using the principle of double effect when certain conditions are met. Furthermore, the safeguarding of informed consent may prove problematic if contraception is integrated with established vaccine programs. (shrink)