Which of the following is NOT a factor affecting immunity?

• A. Previous exposure/natural infection
• B. Vaccination status
• C. Weather
• D. Nutrition

Answer: (C)

Immunity is shaped by prior encounters with pathogens and interventions that train the immune system, along with nutrition that provides the essential resources for immune cell function and barrier defenses. Previous exposure or natural infection builds immune memory, while vaccination primes specific protective responses without causing disease. Nutrition directly supports the development and function of immune cells and the production of antibodies. Weather, by contrast, can influence when or how often people encounter pathogens or how pathogens survive in the environment, but it does not directly alter the immune system’s capacity to respond. So weather is not a direct factor affecting immunity, whereas exposure history, vaccination status, and nutrition are.