Vaccine Adjuvants and Delivery Systems: A Comprehensive Review

Adjuvants play a crucial role in increasing vaccination efficacy. While aluminum salts have historically been the most common adjuvants, recent research has turned to new compounds with enhanced adjuvant properties and improved safety. Cutting-edge nanotechnology, leveraging nanoformulations and novel delivery systems, has enhanced efficacy while reducing adverse effects. Microparticles, emulsions, and immunostimulants are now essential tools due to their significant potential for vaccine production. Additionally, advanced drug delivery systems (DDSs) have been developed using sophisticated technologies to expedite and optimize drug and vaccine delivery to specific target sites, thereby maximizing therapeutic efficacy and minimizing systemic accumulation. The latest DDSs offer numerous advantages over conventional drug delivery systems, including heightened performance, precision, and efficiency. These DDSs, comprising nanomaterials or miniaturized devices, feature multifunctional components that are biocompatible and biodegradable, with high viscoelasticity, thereby extending their circulating half-life. This review aims to provide an in-depth and up-to-date overview of adjuvants and technological advancements in vaccine delivery systems.