Vaccine development is the process of creating vaccines that stimulate an individual's immune system to produce immunity against a specific disease. This process involves identifying the antigen (part of the pathogen that triggers an immune response), testing different formulations and delivery methods, conducting preclinical and clinical trials to evaluate safety and efficacy, and obtaining regulatory approval. Vaccine development plays a crucial role in public health by preventing the spread of infectious diseases and reducing the burden of illnesses on populations worldwide.