Scientific studies have shown that when bacteria or viruses invade the human body, the body produces a substance that fights against such bacteria or viruses, which is called an antibody. Different bacteria or viruses produce different antibodies, called specific antibodies. After the disease is cured, these specific antibodies remain in the body, and if the corresponding bacteria or viruses invade the body again, these specific antibodies can protect the body from being harmed by these bacteria or viruses. Prophylactic vaccination is to artificially inoculate a person with a small amount of bacteria or viruses and their metabolites that have been attenuated or inactivated, etc., so as to cause the body to produce specific antibodies or cellular immune responses, thus generating resistance to the pathogen in question.