A vaccine is best defined as:
A vaccine is best defined as immuno-biological product containing all or part of microorganism or its products, synthetic or recombinant antigens, mRNA or viral vector engineered to express antigen, formulated to induce active acquired protective immunity against specific infectious disease or tumor without causing disease itself. It comprises immunogenic principle plus diluents, stabilizers such as sucrose, surfactants, buffers maintaining pH, preservatives like 2-phenoxyethanol preventing bacterial contamination in multidose vials, and sometimes adjuvants aluminum salts, MF59, AS01 enhancing
Ref: WHO Vaccine definition; Plotkin Vaccines 7th ed Ch 1 immunobiological; CDC NIP.