In 2014, the Kenyan Conference of Catholic Bishops, in cooperation with the Kenyan Catholic Doctors Association, alleged that tetanus vaccines provided through a WHO/UNICEF program were tainted with a contragestive agent. Despite the vehement denial by tetanus program coordinators, serious questions arose as to the possibility that such anti-fertility vaccines can be developed and distributed. This presentation utilizes recent publications on the subject to determine what three biological stages can be targeted with anti-fertility vaccines, the current status and trends of their development, and a principled critique of their possible application using a personalist approach to Thomist ethics. It concludes that the decades-long search for an effective anti-fertility vaccine to attack gametogenesis and gamete function continues with few breakthroughs while vaccines attacking post-zygosis—e.g., anti-human chorionic gonadotropin—have been either temporarily or permanently suspended for several years. Those vaccines utilizing a contraceptive action violate the bioethical principles of inseparability, integrity, and totality; while vaccines that terminate pregnancy post-zygosis through a contragestive action violate the bioethical principles of respect for life, non-maleficence, and beneficence.