"From a theoretical standpoint, therefore, the path would seem to be clear. Parents who reject all association with abortion should feel free to refuse vaccination for themselves and for their children. Nonetheless, when this approach is put into practice, many difficulties arise. For example, objectors often face a problem when they attempt to place their children into a school system, whether public or private. School administrators, who have both a moral and legal obligation to protect the health and well-being of their students (as well as their teachers, school administrators, and all who work there), routinely prohibit attendance by children who have not been vaccinated against rubella and other contagious diseases. Many states offer exemptions from immunization requirements; some do not or only for very specific reasons. Thus a state may accept a religious exemption, but may refuse one based on medical concerns if they are deemed unjustifiable. In cases where an exemption is denied, parents find themselves with very few options. The difficulty is heightened for Catholics because there is no official teaching of the Church on the question of whether the use of these vaccines is permissible. There are, it is true, various “probable opinions” issued by respected Catholic theologians and Catholic organizations, but the Church itself has taken no position. Thus Catholic parents who object to immunization with vaccines implicated in abortion can make no appeal to official church teaching, and if they attempt to do so, they are likely to be shown a statement from some recognized Catholic authority that contradicts their views. Can an appeal to conscience serve as a ground for an exemption to vaccination when there is no Catholic teaching on this matter?"