Vaccines consist of one or more biologically derived active ingredients called “vaccine antigens,” which are derived from bacteria or viruses.
To make the vaccine more effective, the vaccine antigen is usually combined with an adjuvant, which is very often an aluminum salt (hydroxide or phosphate). Antimicrobial preservatives may be used to prevent microbial contamination of the vaccine. Stabilizers (lactose, sorbitol, etc.) may be used to maintain the vaccine’s quality throughout its shelf life.