Fish Vaccination: Anything (antigen) derived from a pathogen that when administered to a target animal (fish): elicits a specific protective response against a foreign body = IR (immune response) and specific response must also have a memory component = DOI (duration of immunity). Objectives: Stimulate the immune system in such a way to increase the resistance to disease from subsequent infection by a pathogen. Vaccination is a protection against disease, not necessarily infection Thus, vaccine protect against outbreak of disease but not necessarily carrier. Basis: Fish have a functional immune system similar to mammals (innate & adaptive). Major differences with other vertebrates are that their metabolism and immune response is temperature dependent. An ideal vaccine should be safe, immunogenic, produce similar protection to natural challenge. Rationale: Vaccination is the best method to increase survival rate and profitability in aquaculture when used in combination with several factors which are necessary to guarantee the highest possible survival rate.