According to Dictionary.com, natural immunity, which is sometimes called native immunity, is the body's genetic resistance to certain disease-causing pathogens. Artificial immunity occurs when antibodies develop in response to the presence of a specific antigen, as from vaccination or exposure to an infectious disease.
According to Vaccines.gov, infections are the most common cause of sickness in humans. Every human being has some degree of natural immunity to infectious agents. The first such barrier is the skin, which physically blocks pathogens' access to the body's tissues. Internally, healthy people have an immune system that is capable of defeating many microorganisms found in nature. This immune system is heavily influenced by genetics, and the specific diseases it protects against will vary from one person to another.
Artificial immunity can be induced by vaccinations. The CDC describes artificial immunity in terms of active versus passive. Passive immunity usually involves a transfusion of antibodies tailored to defeat an infectious agent. Active immunity is the result of a patient's immune system being exposed directly to a weakened or dead form of the pathogen and reacting by developing immunity to the agent. This active immunity, whether natural or artificial, is long-lasting and sometimes remains for life.