Vaccines protect animals from infections without causing disease and are considered one of the great successes of modern medicine. Vaccines made of either parts of microbes, whole microbes that have been killed/weakened, or pathogen subunits made up of specific macromolecules (toxins, proteins and polysaccharides) have the ability to induce the protective immune response against pathogens (De Gregorio and Rappuoli, 2012). Thus in orders to control fish vibriosis in aquaculture, the use of fish vaccines have been shown to be a cost-effective and efficient method. Being made up of natural biological materials, fish vaccines are not associated with toxic residues in the tissues of the organism or in the environment.
Vaccines also do not contribute to the growth of resistant strains of bacteria. Fish vaccines can be a good alternative to the use of antibiotics in aquaculture making fish farming more economically feasible and more sustainable.DNA vaccines have several advantages over classical antigen vaccines. Factors like DNA being a stable molecule, relatively inexpensive and easy to produce, and potential for preparing multivalent vaccines have contributed to DNA vaccines being attractive to fish manufacturers (Heppell and Davis, 2000).