Adjuvants are substances added to vaccines and other medications to enhance the body's immune response to the target antigen. Adjuvants work by activating the immune system's cells, which leads to a stronger and longer-lasting immune response and can reduce the amount of antigen required in a vaccine dose. Adjuvants can be made up of various substances, including oils, aluminum hydroxide, and liposomes. Adjuvants have been used in vaccine formulations for over 70 years and are a critical component in the development of safe and effective vaccines.