Vaccines made of own disease agent

Question

Why are vaccines made of own disease agent or of the fragments of it?

Answer 1

The main objective of vaccines is to artificially persuade a specific inital immune response (and the consequent configuration of memory cells and antibodies) concerning a given infection or disease in order to vaccinate the individual in opposition to infections by the pathogenic agent in the future.  Hence each antibody doesn’t act against a variety of antigens but in its place it acts only against its particular antigen, it is essential for the immune system to establish contact in some way with the antigen in opposition to which the immunization is wanted. The reconnaissance of particular molecular parts of every antigen causes the immune system to generate the specific variable portion of the immunoglobulins to attack that specific antigen. So to induce the active immunization it is essential to inoculate into the body small parts of the infectious agent or the agent completely (dead or inactivated).