Microbes of different diseases are always present in our surrounding
environment and we are also prone to coming in contact with persons
suffering from infectious diseases directly or indirectly. But, because
of strong immune system and presence of antibodies against specific
diseases we do not necessarily develop that disease. Immune system of
our body fights back the pathogens entering the body and most often
successfully remove them. In this way our body remains protected
from diseases. Antibodies to fight pathogens may develop in natural way
or may be produced inside body through vaccination.