Vaccine Additives and Excipients

Abstract

The active ingredient(s) included in vaccines are the pathogen-specific immunogens. Inactive ingredients are called excipients. A review of the long list of excipients included in any vaccine quickly reveals that the vast majority represent trace or residual concentrations of substances used during the manufacturing process. Residual substances include all components of the biologic culture medium used to support cell growth during amplification of the active vaccine components; any antibiotics used to prevent culture contamination; substances used to inactivate pathogens or toxins; and chemicals used to extract, purify, and concentrate the vaccine immunogen(s). All of these substances are essentially removed during subsequent manufacturing steps, leaving behind only trace amounts in the final vaccine product. A second group of vaccine excipients are the substances added to the vaccine during the final manufacturing steps. The precise amounts added remain in the final product to serve a specific purpose. Examples include agents used to stabilize the active vaccine component, substances called adjuvants that enhance vaccine immunogenicity, and vaccine preservatives. Every substance listed as an excipient in a vaccine plays a necessary role during manufacturing and production. Excipients necessary for manufacturing that do not serve a function in the final vaccine product are reduced to residual or trace concentrations in the final product.