Vaccine is defined as

Vaccine is defined as

• A. A suspension of killed or modified microorganisms that stimulate an immune response when introduced into the body
• B. Swelling and inflammation
• C. Having no resistance to disease
• D. More susceptible to disease

Answer: (A)

A vaccine is a preparation designed to train the body's immune system to recognize and fight a pathogen without causing the disease itself. It achieves this by introducing killed or weakened (attenuated) microorganisms, or parts of them, so the immune system can mount a response and develop memory cells. When the real pathogen is encountered later, these memory cells enable a faster and stronger defense, often preventing illness or reducing its severity. The other statements describe reactions or states rather than a definition of a vaccine: swelling and inflammation are common signs of an immune response, not a vaccine; having no resistance to disease and being more susceptible to disease describe vulnerability, not a protective preparation.

A vaccine is a preparation designed to train the body's immune system to recognize and fight a pathogen without causing the disease itself. It achieves this by introducing killed or weakened (attenuated) microorganisms, or parts of them, so the immune system can mount a response and develop memory cells. When the real pathogen is encountered later, these memory cells enable a faster and stronger defense, often preventing illness or reducing its severity.

The other statements describe reactions or states rather than a definition of a vaccine: swelling and inflammation are common signs of an immune response, not a vaccine; having no resistance to disease and being more susceptible to disease describe vulnerability, not a protective preparation.