Adjuvants are substances added to vaccines to enhance the body's immune response to the vaccine's active ingredient. They help the immune system recognize and respond more effectively to the pathogen, leading to better protection against diseases. Common types of adjuvants include alum, MF59, and AS03. These additives can improve the duration and strength of immunity, allowing for lower doses of the vaccine or fewer doses overall. Adjuvants are crucial in developing vaccines for various diseases, including influenza and COVID-19, ensuring that vaccines are both effective and efficient in providing protection.