This invention proposes a novel biofilm-based oral vaccine designed to combat pathogens protected by biofilms. By using suspension culture, bacteria are induced to form biofilms on the surface of chitosan microparticles. These are then formalin-inactivated to preserve their antigenicity, creating an oral vaccine. This technology effectively stimulates both humoral and cellular immune responses, leading to increased antibody concentrations, enhanced phagocytic activity, and improved host survival rates. It successfully overcomes the biofilm-mediated immune evasion mechanism, providing cross-protection against a variety of bacteria. Specifically suited for aquaculture, this vaccine offers an innovative, antibiotic-free solution for controlling chronic and recurring infections, thereby improving health management and promoting sustainable development in the industry.