What is the term for the state of being able to resist a disease after exposure to its causative agent?

The term that defines the ability to resist a disease after exposure to its causative agent is "immunity." This concept refers to the body's capacity to recognize and defend against pathogens, such as viruses and bacteria, after having encountered them. Immunity can be achieved through natural infection, where the body develops a response to a specific pathogen, or through vaccination, which introduces a harmless part of the pathogen to stimulate an immune response without causing the disease.

Resistance is a more general term that does not specifically imply the development of a protective response following exposure to a pathogen. An allergy involves an inappropriate immune response to normally harmless substances, which is distinct from immunity. Susceptibility refers to the likelihood of an individual to be affected by a disease, which is the opposite of being immune. Thus, immunity is the most accurate term to describe the state of being able to resist disease following exposure to its causative agent.