Fundamental safety requirements in the use of live vaccine in food animals]

Live vaccines have a number of advantages over inactivated ones--above all in respect of the stimulation of cell-mediated immune reactions. Various live vaccines, based on viruses, bacteria, fungi or parasites, have been approved for use in Germany in animals used as a source of food. Safety requirements obviously play a more important role for live vaccines, both in vaccine development and in batch testing, than with inactivated vaccines. Vaccine strains isolated from tissue samples must be clearly distinguishable from field strains. The safety of overdoses and the spread of the vaccine strain in the immunized animals have to be investigated, as well as shedding of the vaccine strain and its safety in non-target species. Any impact of a live vaccine strain on humans and the environment must be assessed. Live vaccines will remain an important research field in the long term, with efforts focused on developing deletion mutants and vector vaccines.