Microbiology
To enhance the magnitude and quality of the immune response (e.g., increase antibody titers, prolong antigen presentation, and stimulate helper T cell activation) because the nonreplicating vaccine lacks amplification.
To act as an antibiotic preservative ensuring the vaccine kills any contaminating bacteria during storage, which is its only immunological effect.
To conjugate polysaccharide antigens to carrier proteins so they always behave as T-dependent antigens in all formulations.
To provide nutrients to the vaccine to enable it to replicate after injection and produce more antigen in vivo.
