The application of the precautionary principle to the blood system: the Canadian blood system's vCJD donor deferral policy.

The precautionary principle is an influential concept that has been widely used in international treaties and declarations involving the protection of the environment. The principle is now being applied to the development of transfusion policy. In this article, we examine the application of the precautionary principle in the policy process leading to Canada's decision to defer donations from individuals who had traveled to the United Kingdom because of concerns over variant Creutzfeldt-Jakob disease. We found that, although the principle prominently influenced the decision-making process, problems existed with its interpretation. In particular, there was difficulty in balancing the risk prevented by applying a precautionary measure against the risk introduced by the same measure; in this case, the potential for shortages of blood. This dilemma is somewhat unique to the public health sector and will likely recur in future applications of the principle to transfusion policy.