Viral Vaccines Joseph L. Melnick As with history in general, the history of vaccines needs to be reexamined and updated. My task is to look back to see what has been successful and to look forward to see what remains to be accomplished in the prevention of viral diseases by vaccines. Also, I shall refer to the pertinent material discussed at two recent conferences of the Institute of Medicine, National Academy of Sciences, on virus vaccines under development and their target populations in the United States (1985b) and in developing countries (1986). These reports, plus a third on Vaccine Supply and Innovation (1985a), should be required reading for all those in both the public and the private sector who have a responsibility or interest in vaccines for the prevention of human disease. It has been through the development and use of vaccines that many viral diseases have been brought under control. The vaccines consist either of infectious living attenu- ated viruses or of noninfectious killed viruses or subviral antigens. When we look at the record, it is the live vaccines that have given the great successes in controlling diseases around the world. Examples are smallpox, yellow fever, poliomyelitis, measles, mumps, and rubella.