The article reviews the mechanisms by which adjuvants enhance immunity to vaccines and experimental antigens. Adjuvants, which are used to improve the effectiveness of vaccines, can influence both the magnitude and quality of the adaptive immune response. The review highlights how adjuvants engage components of the innate immune system, such as pattern recognition receptors (PRRs), to enhance T and B cell responses. It discusses the challenges in developing adjuvants that generate strong T cell immunity with purified or recombinant vaccine antigens, particularly for diseases like HIV/AIDS, malaria, and tuberculosis. The article also explores the use of codelivery of antigens and PRR ligands, the importance of multiple innate stimuli, and the safety considerations associated with adjuvant use. Overall, the review emphasizes the need for a better understanding of the cellular and molecular mechanisms of adjuvants to develop more effective vaccines.The article reviews the mechanisms by which adjuvants enhance immunity to vaccines and experimental antigens. Adjuvants, which are used to improve the effectiveness of vaccines, can influence both the magnitude and quality of the adaptive immune response. The review highlights how adjuvants engage components of the innate immune system, such as pattern recognition receptors (PRRs), to enhance T and B cell responses. It discusses the challenges in developing adjuvants that generate strong T cell immunity with purified or recombinant vaccine antigens, particularly for diseases like HIV/AIDS, malaria, and tuberculosis. The article also explores the use of codelivery of antigens and PRR ligands, the importance of multiple innate stimuli, and the safety considerations associated with adjuvant use. Overall, the review emphasizes the need for a better understanding of the cellular and molecular mechanisms of adjuvants to develop more effective vaccines.