What does a vaccine do?

A vaccine is designed to stimulate a person's immune system, leading to the production of immunity against specific diseases. When a vaccine is administered, it often contains weakened or inactivated parts of the germ that causes a disease, or a blueprint for producing antigens. This exposure trains the immune system to recognize the pathogen, allowing the body to mount a more effective response upon actual exposure to the disease in the future.

This process is crucial for achieving immunity, as it prepares the immune system to recognize and fight off infections more effectively, potentially preventing illness. The primary purpose of vaccines is thus to enhance the body's natural defenses and provide protection against specific pathogens, rather than simply acting as treatment for pain or guaranteeing prevention of all diseases.