Why are adjuvants used in vaccines?

• A. To make the vaccine ingredients more soluble.
• B. To avoid undesirable side effects.
• C. To stabilize the antibody serum titer.
• D. To enhance the immune response.

Answer: (D)

Adjuvants are added to vaccines to boost the body's immune response to the vaccine antigen. They do this by stimulating the innate immune system, attracting and activating antigen-presenting cells, and often extending the duration the antigen is available, which leads to a stronger and longer-lasting adaptive response. This can result in higher antibody levels and better cellular immunity, and it can even allow using smaller amounts of antigen.

The other ideas aren’t the primary purpose: making vaccine ingredients more soluble is a formulation concern, avoiding side effects isn’t the goal and adjuvants can sometimes increase reactogenicity, and “stabilizing” antibody titers isn’t the intended function—adjuvants mainly enhance the magnitude and durability of the immune response.