Resistant immunity refers to the body's ability to defend itself against specific pathogens, such as bacteria and viruses. This immunity can be acquired through previous infections or vaccinations, which help the immune system recognize and respond more effectively to future encounters with the same pathogens. There are two main types of immunity: innate immunity, which is the body's first line of defense and responds quickly to any invader, and adaptive immunity, which develops over time and provides long-lasting protection. Vaccines, like those for influenza or COVID-19, stimulate adaptive immunity by training the immune system to recognize and combat specific pathogens.