Immunity is defined as?

• A. The body's ability to destroy infectious agents that enter the body
• B. A measure of antibodies in the blood
• C. A condition of complete resistance to all pathogens
• D. The process of producing vaccines

Answer: (A)

Immunity means the body's ability to resist and destroy infectious agents that enter the body. This ability comes from the immune system, including frontline innate defenses (like skin, mucous membranes, and phagocytes) and the adaptive response (specialized cells and antibodies that target specific invaders and remember them for faster future responses). It’s not simply a measure of antibodies in the blood, nor does it imply complete resistance to all pathogens. Vaccines are a way to build immunity by training the immune system to recognize particular pathogens, but producing vaccines is not immunity itself.