New adjuvants for human vaccines

Despite their obvious benefits, decades of research and hundreds of pre-clinical candidates, only a handful of adjuvants are approved for prophylactic vaccination of humans. The slow pace of development is due to a number of knowledge gaps, the most important of which is the complexity involved in designing adjuvants that are both potent and well tolerated. Recent advances in our understanding of innate immunity have led to the identification of immune pathways and adjuvant formulations more suitable for clinical advancement. One area of particular interest is the discovery of agonists that target the toll-like receptors. This review highlights recent progress of clinically approved vaccine adjuvants and identifies potential novel adjuvants that can broaden the development of new vaccines against infectious diseases.