Vaccination is a very familiar term to us. Every newborn is recommended to follow a vaccination/immunisation schedule. Yet, many of us do not know what vaccines really are or how they prevent diseases.
It is part of folk knowledge that measles, if contracted once, will never appear again. Ever wondered why this is so? The answer to this mystery lies within our adaptive immune system. Mediated by white blood cells known as Lymphocytes, the adaptive immune system enables us to develop immunity against the specific bug that has infected the body. Not only that, it also creates a 'memory' of the infection/bug. Thus, subsequent infections are quickly identified and dealt with before it manifests as a disease. Just imagine how the nation’s defensive forces manage to diffuse security threats without much collateral damage whenever intelligence bureaus and such agencies provide them with information before hand. The preparedness makes them invincible most often. One may say the same applies to the immune system as well.
Vaccines are either inactive bugs or bug-like bodies which induce a response from adaptive immune system. Thus when the real pathogen infects the body, the lymphocytes and hence the immune system, would be prepared to tackle the situation. In other words, vaccines help us acquire bug-specific immunity. Inactive pathogens and pathogen-like bodies pose no real threat to us either, making vaccination a very efficient and safe preventive measure. On any day, 'prevention is better than cure'.