Which statement best describes how vaccines can achieve lasting immunity?

• A. By inducing memory B and T cell responses
• B. By permanently activating all immune cells
• C. By removing all antigens from the body
• D. By triggering constant inflammation

Answer: (A)

Memory formation in the adaptive immune system is what makes vaccines give lasting protection. A vaccine presents antigen in a safe way, so B cells that recognize it proliferate and become plasma cells and memory B cells, while T cells differentiate into helper and cytotoxic cells and later form memory T cells. This creates a reserve of long‑lived memory cells that stay ready and can respond quickly if the real pathogen shows up, producing high‑affinity antibodies and rapid cellular responses. Booster doses help enlarge and sharpen this memory, strengthening how long the protection lasts. In contrast, permanently activating all immune cells would risk autoimmunity, removing antigens after vaccination isn’t how lasting immunity is built, and continually triggering inflammation would cause harm without providing targeted, durable protection.