When the immune system first sees an infectious microbe, it responds against it and then remembers it specifically. So the next time that particular microbe, or its close relatives enter the body, the immune system responds with even greater vigour. This eliminates the infection even more quickly than the first time around. This is the basis of the principle of immunization.Vaccines work on the principle of immunization. Vaccines help a body\’s immune system prepare in advance to fight infectious illnesses and potentially deadly diseases caused by infectious agents or their by-products. Vaccines ‘fool’ the immune system into developing a memory for a particular infection by putting something that mimics the microbe we want to vaccinate against, into the body.