Apicomplexan parasites or red blood cells infected with apicomplexan parasites are administered to an animal in combination with a delayed death agent that initially allows parasite replication but subsequently kills the apicomplexan parasites. This allows the elicitation of an immune response by the animal while preventing the parasites producing a serious infection of the animal. The apicomplexan parasites may be malaria or babesia parasites. The delayed death agent may be a tetracycline class antibiotic, a macrolide antibiotic or a lincosamide antibiotic.