Immunization makes a person resistant or immune to a disease by administering a vaccine into the body. This action causes the immune system to recognize viruses and bacteria that cause infection or disease and react by producing antibodies, according to MedicineNet.
When a person gets sick, the body responds by producing antibodies against the antigens that cause the disease. After recovery, the antibodies remain active in the body and protect the person from the same disease in the future. Immunization attempts to replicate this process without causing illness. In the immunization process, a patient introduces a small portion of a dead or weakened organism that causes a certain disease. Rather than causing harm in the body, this weak organism forces the immune system to produce antibodies that can act against the real organism that causes the specific disease, reports WebMD.