Vaccines, adjuvants and conventional methods of using them in farmed fish

Fish immunization using vaccines has been practiced for more than 50 years and is generally accepted as an effective method for preventing a wide range of bacterial and viral diseases. Vaccination contributes to environmental, economic and social sustainability in global aquaculture. Most of the manufactured vaccines are inactive vaccines that are formulated using adjuvants and delivered to fish through injection, immersion or oral routes. Live vaccines are more effective than inactivated vaccines because they mimic the conditions of natural pathogen infections and elicit a strong antibody response. Unfortunately, vaccines are usually not able to provide protection on their own. Especially those vaccines that are based on recombinant antigens or inactive pathogens. Therefore, the use of adjuvants or immunostimulants is often necessary to increase vaccine efficacy and have more potential to be administered through injection, oral or immersion routes. Nowadays, new vaccines (mucous and toxoid) and herbal adjuvants have been more and more noticed by researchers and have had significant effects against infectious diseases. Advanced technologies hold promise for the future of aquaculture vaccines, providing health benefits and increased economic potential for producers. Considering that vaccines have protective and preventive functions against a wide range of diseases, in this article we discussed the types of vaccines and aquatic adjuvants and their methods of use.