Answer the following question:
The principle of vaccination is based on the property of the "memory" of the immune system. Taking one suitable example, justify the statement.
The principle of vaccination is based on the property of 'memory' of the immune system. In vaccination, a preparation of antigenic proteins of the pathogen or attenuated (inactivated/weakened) pathogen is introduced in the body. The antibodies produced in the body against these pathogens will neutralize the pathogenic agents during actual infection. The vaccine also generates memory B-cells and T-cells that recognize the pathogen quickly on subsequent exposure. For example, vaccination against polio prevents the actual pathogen from resulting in infection.