The major goals of veterinary immunization are to improve the health and welfare of animals, increase production of livestock in a cost-effective manner, and prevent animal-to-human transmission from both domestic animals and wildlife. The veterinary immunization techniques have a major impact on animal health and production and also have a major influence on human health through increasing safe food supplies and preventing animal-to-human transmission of infectious diseases. These various aims have led to different approaches in the development of veterinary vaccines from crude but effective whole-pathogen preparations to molecularly defined subunit vaccines, genetically engineered organisms or chimeras, vectored antigen formulations, and naked DNA injections. The final successful outcome of vaccine research and development is the generation of a product that will be available in the market. Considerable progress has been made in the production of vaccines whether live or inactivated for animal use during the past two decades with the increasing use of continuous cell lines as a substrate and adoption of the fermenter technology for antigen production. These vaccines are produced for administration to domestic animals or wild species by parenteral or oral routes according to vaccine characteristics. Successful veterinary vaccines have been produced against viral, bacterial, protozoal, and multicellular pathogens, which in many ways have led the field in the application and adaptation of novel technologies. The continued interaction between animals and human researchers and health professionals will be of major importance for adapting new technologies, providing animal models of disease, and confronting new and emerging infectious diseases.