Natural active and non-natural active immunization

Question

What are natural active immunization and non-natural active immunization?

Answer 1

Natural active immunization is that in which a prior general infection persuades the initial immune reaction, specific memory cells are made and the individual becomes immune to new infections with the antigen. That’s what happens in diseases that affect people only one time in life, like mumps and chickenpox. Artificial active immunization is that in which the inital immune reaction is caused by the inoculation in an particular specially prepared antigens. This is in the case of vaccines.