Answer:
Paul has natural active immunity, while Nicholas has artificial active immunity.
Explanation:
Natural active immunity is an immunity that occurs when an individual is exposed to a disease causing organism, gets infected, and also become immune to the disease due to the primary immune response. From the question, Paul has natural active immunity because he had chicken pox before, and the virus that causes chicken pox has interacted with his immune response, hence, making him to develop natural immunity to the disease.
Artificial active immunity is an immunity that an individual acquires when small amount of immunity to a disease is deliberately exposed to his body. Artificial active immunity is usually produced in the form of vaccinations. From the question, Nicholas has artificial active immunity because chicken pox vaccines were intentionally introduced to his body.
