The development of recombinant vector vaccines will be guided by nearly two centuries of research in vaccinology and immunology. Experimental vector vaccines may be of viral, bacterial or genetic composition and their acceptability will depend on safety, efficacy, and practicality as seen by the user, the developer, and the licensing authority. Recombinant vector vaccines will need to compete with alternative vaccine approaches and may find special use for non-propagable agents, immunization in early life, fertility control, and emerging infectious agents. Needs of the developing nations that include low cost, temperature stability, and ease of administration may be met, in part at least, by the vector vaccine approach.