It is indisputable that there is a significant and costly disparity between the number of patients who require an organ transplant and the number of organs currently available for transplantation. The desire to support or promote xenotransplantation as part of the solution to this shortage is understandable but the implications of doing so must be acknowledged and addressed because ‘[a]dvances which may seem to be the answer to a pressing problem may well entail consequences of such a drastic nature as to cause researchers to halt and take stock of their situations before proceeding further’. The science behind xenotransplantation continues to develop and although some of the initial barriers to placing a non-human animal organ into a human appear to have been addressed, it remains unclear whether a solid organ xenotransplant will be able to support a human life. In addition, performing such a transplant may transfer infectious diseases across the species boundary to the xeno-recipient and others, and it is this risk which requires global legal and regulatory attention. While porcine endogenous retroviruses have been the main focus to date, it is anticipated that other organisms will need investigating and that latent diseases may be transmitted to the xeno-recipient and others. These risks and their unknown nature and magnitude make xenotransplantation a useful case study through which to explore the role of science in society, public involvement in science and decision-making, risk, responsibility (individual, societal, governmental), regulation, public health and the global ‘market’. These themes have underpinned the discussions within this book, along with the idea that developing biotechnologies may pose challenges to established legal and ethical norms.

In Chapter 2, I explored the risks posed by genetically engineered solid organ xenotransplants and argued that in situations of uncertainty a precautionary approach informed by the harm principle is an appropriate response because where the risk is significant with regard to the probability of transmission and the severity of harm, action should be taken to prevent harm to public health. This approach is required because ‘[t]oo often . . . public health and environmental policies are based on a principle of reaction rather than precaution’ with regulatory agencies ‘having to wait until evidence of harm is established beyond all reasonable doubt before they can act to prevent harm’. Adopting a precautionary approach does not necessarily mean that such xenotransplants cannot be performed, but it does require society to consider whether it is appropriate to proceed to clinical use when possible individual benefit may place public health at risk. Xenotransplantation is thus a useful reminder that health care involves protecting and enhancing the health of individuals and that of the public, and that ‘a shift from reaction to precaution is entirely consistent with the core values of public health practice’. The UK government has acknowledged the importance of public health and commented that: