Immunity is the ability of the human body or other living beings to resist invasion by pathogenic agents, such as viruses, bacteria, fungi and parasites, or to neutralize toxic substances. Immunity is a response from the immune system, which is responsible for protecting the body against disease and infection.

The immune system is made up of cells, tissues and organs that work together to recognize, fight and destroy invading agents and foreign substances. When the immune system is able to protect the body against an infection, the person is said to be immune to the disease.