True or False: Disease is prevented by prior exposure to an attenuated or killed infectious agent.

The assertion that disease is prevented by prior exposure to an attenuated or killed infectious agent relates to the principles of vaccination and immune response. When a person is vaccinated with an attenuated (live but weakened) or killed (inactivated) version of a pathogen, their immune system recognizes these agents as foreign, triggering an immune response.

This immune response leads to the activation of specific immune cells and the production of antibodies. Importantly, this "training" of the immune system helps it respond more effectively and quickly if the individual encounters the actual pathogen in the future, thereby preventing disease.

However, the statement’s evaluation as 'False' implies that exposure to an attenuated or killed infectious agent does not universally prevent disease. There are several factors to consider. Not every individual will reach protective immunity after vaccination due to variations in immune response, the completeness of vaccination schedules, or the presence of underlying health conditions that may affect immune function.

Moreover, while attenuated and killed vaccines have been highly successful for many infections, certain pathogens and diseases may not be effectively prevented by these means, and alternative strategies like subunit vaccines or mRNA vaccines may be necessary.

In conclusion, the statement is judged as false because it overgeneralizes the efficacy of immunization strategies across