###### Abstract  
Aquaculture is rapidly becoming one of the pivotal sectors in the farming economy, driven by the increasing demand for high-quality animal protein at an affordable cost, especially with the escalating human population. However, the expansion of high-density fish populations also brings forth a challenge--the rapid transmission and spread of infectious disease agents among them. To combat this, vaccination is emerging as a reliable and standardized method for providing immunity against viral and bacterial outbreaks. The ideal vaccine is expected to be safe, effective, economical, and easily administered. The fish vaccination industry continually publishes new information on fish immunology and vaccinology, contributing to the improvement in vaccine formulation and efficacy. This review aims to offer insights into the current status of bacterial, viral, and parasitic diseases, discuss existing vaccinations, and address potential industry-threatening diseases like infectious edwardsiellosis, motile aeromonas septicemia (MAS), Tilapia Lake Virus (TiLV) disease, infectious salmon anemia (ISA), vibriosis, and white spot disease. Technological advancements have played a crucial role in enhancing our understanding of fish immunological mechanisms, leading to improved vaccine administration and the development of recombinant live attenuated, subunit, DNA, and RNA vaccines. However, challenges such as oral tolerance, vaccine degradation, and stressful environments persist, impacting vaccine efficacy. Addressing these challenges and gaining a deeper understanding of the fish immune system and host-pathogen interactions will be pivotal for future improvements, contributing to the sustainability of aquaculture and enhancing global food security. a quaculture; infectious diseases in fish; fish vaccination; fish pathogens; fish immunology; bacterial; viral and parasitic diseases in fish; fish vaccines; technologies +
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infectious salmon anemia alone resulted in the loss of 20,000 jobs, costing the country USD 2 billion [6]. China, the producer of 70% of the world's farmed fish, experiences a 15% loss in total fish production due to diseases [7]. Hence, there is a significant emphasis on developing methods to prevent and control the spread of diseases. In the early stages, antibiotics served as a primary tool to combat infections due to their accessibility, affordability, and effectiveness in treating bacterial diseases. However, the repeated use of antibiotics was observed to suppress the fish's immune system and induce antibiotic resistance, thereby posing a threat to consumer health and safety [8; 9]. As an alternative approach, vaccinations were introduced to decrease reliance on antibiotics. The initiation of fish vaccinations dates back to the 1940s, and since that time, vaccines have played a pivotal role in mitigating the impact of bacterial and viral diseases on fish [10; 11]. In the 1980s, only two commercial fish vaccines were available [1]. Presently, the market boasts over 50 vaccines catering to more than 30 different fish species. A majority of these vaccines have received approval from the United States Department of Agriculture (USDA) and are produced using methods that involve culturing target pathogens [12; 13]. Administration primarily occurs through intraperitoneal injections. Ultimately, vaccination has proven highly successful, annually safeguarding thousands of fish from severe diseases [1]. When discussing the design and application of fish vaccination, it is important to have a good understanding of the fish immune system. Typically, the vaccination process involves trial-and-error with regard to pathogen identification, cultivation, and vaccine formulation [14].