The body’s immune system helps protect against pathogens that cause infection. Most of the time, it’s an efficient system. It either keeps microorganisms out or tracks them down and gets rid of them.However, some pathogens can overwhelm the immune system. When this happens, it can cause serious illness.The pathogens most likely to cause problems are the ones the body doesn’t recognize. Vaccination is a way to “teach” the immune system how to recognize and eliminate an organism. A healthy immune system defends against invaders. The immune system is composed of several types of cells. These cells defend against and remove harmful pathogens. However, they have to recognize that an invader is dangerous.Vaccination teaches the body to recognize new diseases. It stimulates the body to make antibodies against antigens of pathogens. It also primes immune cells to remember the types of antigens that cause infection. That allows for a faster response to the disease in the future.