Implications of a vaccine for the prevention of Epstein-Barr virus infection: ethical and logistic considerations.

Reasons are given for considering that there is sufficiently substantial indirect and circumstantial evidence linking Epstein-Barr (EB) virus to African Burkitt's lymphoma (BL) and nasopharyngeal carcinoma to call for a dynamic new approach to establish a causal role for the virus in these human cancers. It would seem that the only way to do this would be to develop a vaccine, vaccinate a population at risk in a high-tumor-incidence area, and subsequently follow the population for a consequential decrease in tumor incidence. Recent developments in the control of animal herpesvirus-induced malignant tumors by vaccines free of viral nucleic acid make it possible to envisage that a similar vaccine could be developed against EB virus without undue difficulty. Experiments showing the tumor-inducing ability of EB virus in South American subhuman primates have provided an in vivo laboratory system in which to test the safety and efficacy of the vaccine. Trial of the vaccine in human populations could be carried out by testing its ability to protect those at risk from primary EB virus infection accompanied by infectious mononucleosis. Although in world terms BL is not a major health problem, nevertheless African BL provides uniquely favorable conditions in which to test for a causative role for EB virus: high incidence areas are known, the peak tumor incidence is at the age of 5 or 6, and the effects of vaccination on tumor incidence could be assessed within a decade. Should a carcinogenic role for EB virus be demonstrated in African BL, a much longer term program would be called for to extend the vaccine control of infection to areas where EB virus is implicated in the induction of nasopharyngeal carcinoma. Although a high incidence of this tumor is confined to populations of Southern Chinese origin, the very large numbers of such people and the frequency of the tumor among them make this a substantial world health problem and, therefore, worth the cost and effort necessary to develop a vaccine giving life-long immunity and to conduct a program that will take more than a generation to give positive results.