Disease outbreaks and consequential losses are a challenge to the aquaculture industry. Diseases in aquaculture are caused by pathogenic agencies, such as bacteria, viruses, and parasites. The use of vaccines is one approach for the control of infections in fish and in building immunity against them. The goal of the present study was to create an effective oral vaccination against V. harveyi in order to ensure the long-term viability of aquaculture operations in the Sultanate of Oman. At a commercial farm, the tar get bacterium was isolated from infected fish and identified from a pure strain. Bacteria were killed with formalin and cleaned with saline several times. The vaccine was mixed with commercial feed to provide an oral vaccination for fish. This vaccinated feed was given for four weeks, and the efficiency of vaccine was determined by a challenge test, which involved injecting live same species of bacteria into healthy fish. Histology samples were taken when the experiment was completed. Multivitamins and vaccination therapy helped the fish to develop faster and to survive for extended periods of time without any organ damages. The control fish, on the other hand, demonstrated an incapacity to resist bacteria and died as a result, with external and internal organ damage. Despite the positive findings of this study, more research is required.