43 speakers and presenters and more than 200 participants. The workshop focused on three major topics: the science base; the public health risks of infectious disease transmission; and the ethical and public policy issues, including the views of patients and their families. Based on this workshop and additional deliberations, the committee came to specific conclusions and made recommendations, which are outlined here and summarized in detail in the full report.

Recommendation 1

There is ample evidence for the transmission of infectious agents from animals to humans. Transmitted organisms benign in one species can be fatal when introduced into other species. Because xenotransplants involve the direct insertion of potentially infected cells, tissues, or organs into humans, there is every reason to believe that the potential for transmission of infectious agents (some of which may not even now be recognized) from animals to human transplant recipients is real. Once an infection is established in the recipient, the potential for transmission to caregivers, family, and the population at large also must be considered a real threat. The committee concludes that, although the degree of risk cannot be quantified, it is unequivocally greater than zero. Hence, the committee recommends that guidelines for human trials of xenotransplantation address four major areas: (1) procedures to screen source animals for the presence of infectious organisms and consideration of the development of specific pathogen-free animals for use in xenotransplants; (2) continued surveillance throughout their lifetimes of patients and periodic surveillance of their contacts (families, health care workers, and others) for evidence of infectious diseases; (3) establishment of tissue banks containing tissue and blood samples from source animals and patients; and (4) establishment of national and local registries of patients receiving xenotransplants. Special efforts should be made to coordinate with international registries and databases.

Recommendation 2

The committee discussed various alternatives for oversight or regulation of clinical trials in light of the risk of transmission of infectious agents to the general population from xenotransplantation. Several committee members felt strongly that special regulation of xenotransplant research is not justified because other types of research, including allotransplantation, also involve substantial risks. Other members of the committee argued that the potential for

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