Although most prominent, infection is not the only risk presented by xenotransplantation. For example, some transplant surgeons and others fear that too much publicity about xenotransplantation will decrease public willingness to donate organs, even though the technology is years away from providing a practical resolution of the needs of people who require whole organ transplants. Still others are concerned that clinical practice may forge ahead despite the absence of an adequate scientific base, which happened, for example, with in vitro fertilization.4 In addition to the adverse effects of immunosuppression and the vascular damage that can accompany allotransplantation, there are risks that xenotransplantation may have negative effects on the quality of life of recipients, despite providing a medically effective outcome. There is also uncertainty about the eventual expense of xenotransplantation—a complex issue that will be a critical determinant of the extent of eventual use of various types of xenotransplantation and must be considered in light of any eventual savings (e.g., decreased health care expenditures for diabetics with xenotransplants of pancreatic islet cells; also see Chapter 4).

Important ethical and social issues regarding xenotransplantation need extensive further consideration. Indeed, some of these issues have not yet been resolved for human-to-human organ transplantation. How will animal and human organs be allocated? Will socioeconomic status influence allocation, so that the affluent and powerful are more likely to receive human organs, while the poor and disenfranchised receive animal organs? Should animals be killed to provide organs? Are there fundamental psychological factors that will lead to problems for recipients of animal organ transplants? People who have received human organ transplants often report having deep and complex emotions about having another person's organ in their bodies. Will this be magnified in people who receive animal organs? Will the expense of xenotransplants outweigh the benefits?

Questions such as these were raised throughout the workshop and in the deliberations of the committee amidst discussion of significant scientific progress and hope for the potential benefits of xenotransplantation. The issue of public health risks, however, clearly dominated and molded these discussions. As a result, the report that follows presents many scientific and ethical issues interwoven with scientific discoveries and hypotheses, which raise both familiar and novel ethical and legal issues at the frontier of medical innovation.


The success rate of in vitro fertilization remains only about 20 percent in the best facilities, in part because the growth of the science base has been seriously hampered by political and ethical debates concerning abortion and research on human embryos.

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