"After all of this has been said, if one judges that the use of these vaccines is indeed morally coherent for those who condemn abortion, even if it is not unqualifiedly desirable, one must be prepared for a further challenge. If the use of these vaccines despite their connection with abortion were to become customary, and if people cease to be uncomfortable with the regrettable origins of these vaccines, it will probably become more difficult to maintain the distinction between the use of existing fetal cell lines for vaccines and the use of fetal tissue for research and transplantation, not to mention the various experimental uses of frozen human embryos. The distinction articulated above—between a noncomplicit, accidental relationship and an association that is incoherent with principled opposition to abortion—will probably become more difficult to defend in public. As the practice of fetal tissue research and transplantation spreads, the sorts of arguments presented above are likely to be recast and used in support of this sort of research and transplantation.47 This suggests that it is rhetorically difficult to display the moral coherence of using these vaccines while simultaneously opposing proliferation of the therapeutic use of aborted fetal tissue. This difficulty is not decisive for the question of vaccines, but neither is it irrelevant. Whatever the future may hold in this regard, it is essential to think seriously about the moral significance of these matters. It would be irresponsible to condemn vaccines and other powerful therapies for superficial or accidental moral reasons. The health benefits at issue are considerable, and weighty moral reasons must be given before it is coherent to accept what may be a serious loss of control over vaccine-preventable diseases."