It will be important to tailor the vaccination regime to normal farm management procedures for the target species, and to deliver vaccines at an acceptable cost. There is considerable scope for improving vaccine delivery. First, the vaccination schedule should not impose significant management constraints on the producer, over and above those associated with current control practices. As an example, the conventional method of delivering a live coccidiosis vaccine to chickens was through their drinking water, or by spraying the vaccine onto their feed. To facilitate broiler production management, these vaccines are now preferably administered by spraying the chickens at one day of age. In the future, administration in ovo is a clear possibility (52). Secondly, alternatives have been developed to replace the use of needles for vaccines that must be administered parentally, such as DNA vaccines (21). These alternative devices can also be used to administer conventional vaccines, and are convenient in pig farming. Oral and mucosal delivery systems are also being exploited (for example, delivering vaccines to grazing ruminants in their forage is one exciting possibility) (1, 51). Vaccines are preferably delivered as a single shot, i.e. not requiring repeated booster vaccinations, to reduce the costs of animal handling and veterinary services. Different delivery systems, such as microspheres, liposomes, pumps and implants, have been