The human immune system is a system of biological structures and processes that protects us against diseases by recognising germs that enter the body as foreign invaders. These are referred to as antigens, a term which stands for “antibody generator”. When antigens invade the human body, the immune system responds by producing protein substances called antibodies and highly speci?c cells that can fight the invading germs.
Immunity is the body’s successful defence against a pathogen. When a sufficient number of antibodies has been produced by the body to fight the disease, immunity results, providing protection against the disease for many months, for years or even for a lifetime. If a person later comes into contact with that same pathogen again, the immune system will be able to quickly produce the same type of antibodies preventing the disease from developing or decreasing its severity and eliminating the pathogen from the body. Through “immunological memory”, it is estimated that the immune system can remember or recognise and effectively combat hundreds of thousands, possibly millions, of different organisms.
Vaccination involves the introduction of a limited quantity of a specific disease antigen into the human body stimulating the immune system just enough to produce the amount of antibodies needed.