How can a vaccine protect you against a disease?

A Vaccine is a small amount of antigen injected in an individuals body,in response to which antibodies are produced in the body.Antigen is an agent that resembles small dose of disease causing microbes or their toxins.As antigen is injected the body starts producing antibodies,which are bodies immune receptors that invade against the antigen.The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters or it comes in contact with.

I completely agree with you Deergha.. Vaccination is available for a number of diseases. It should be given to the children in required doses during early childhood so as to protect them from many hazardous diseases.