Current use of antimicrobial preservatives in multi-dose vaccines and biologics

Antimicrobial preservatives (APs) offer significant advantages when included in multi-dose vaccines (MDVs) and biologics. In addition to reducing medical waste and optimizing overall manufacturing efficiency, MDVs with APs increase global access to critical medicines and meet public health demands. Phenol, metacresol, benzyl alcohol, benzethonium chloride, thimerosal, and phenoxyethanol are currently the only APs included in FDA-approved biologics and WHO prequalified vaccines. The mechanisms of actions of these six APs, however, may limit their suitability for certain biologics, namely RNA-based vaccines. Novel antimicrobial agents, such as zinc salts and chitosan, may be considered for further investigation and potential use as alternative APs. Including APs in biologics gives rise to additional manufacturing considerations pertaining to drug product quality and stability. In addition, antimicrobial agents have not yet been tested or approved for use in RNA-based vaccines, which highlights important implications for access and shelf-life.