What is the purpose of a vaccine?

The purpose of a vaccine is to provide immunity to disease. Vaccines work by training the immune system to recognize and combat pathogens, such as viruses or bacteria, without causing the disease itself. They stimulate the body's natural defenses to build up a protective response, which may include the production of antibodies. This allows individuals to be better prepared to fight off specific infections in the future.

In contrast, treatments for existing diseases focus on managing symptoms or eradicating an ongoing infection, which is not the role of a vaccine. Alleviating symptoms of illness does not prevent the disease from occurring and typically requires different interventions. While physical fitness is important for overall health, it is not the objective of vaccines, which are specifically designed to promote immunity against infectious diseases.