Rationales for including adjuvants in vaccines

The majority of vaccine antigens in the industry pipeline are relatively poor inducers of adaptive immunity unless effective adjuvants are coadministered. Adjuvants based on aluminium salts have been the only approved and available adjuvant for almost a century. However, although alum effectively promotes humoral immunity, it is not effective for diseases where cell-mediated immunity is required for protection. Moreover, other particulate adjuvants are superior to alum in promoting antibody responses to pandemic influenza antigens. There has been considerable progress in the discovery of novel antigens, which is facilitating vaccine development for currently intractable and new diseases, including therapeutic indications. Hence, especially when cell-mediated immune responses are required, these antigens demand a new generation of adjuvant, which can drive and specifically direct the desired immune responses. In parallel, increased understanding of immunology and, particularly, innate immune sensing is informing vaccine adjuvant research and driving the development of novel and specifically targeted vaccine strategies. In this concise chapter we address the importance of adjuvants in the important field of modern vaccine developmen