On January 24, 1823, the British medical scientist chener died. Qinna uncovered the mystery of cowpox and eliminated smallpox. Smallpox is an infectious disease. Vaccinating against cowpox is vaccinating. So why vaccinate?

Vaccination, also known as vaccination, is one of the most economical and effective methods to prevent and control infectious diseases. Vaccination can enhance the immune capacity of the body, improve its own resistance, resist the invasion of bacteria, and thus play a role in protecting the human body. Therefore, everyone will be vaccinated in a planned way after birth. Infectious diseases such as hepatitis B, measles and polio have been controlled through planned immunization.

Why vaccination can prevent infectious diseases? It turns out that the human immune system has memory function. Vaccine is also a pathogenic agent, but its toxicity to human body is low. After the human body is vaccinated, the immune system will produce corresponding antibodies to fight it, showing slight reactions, such as swelling, local ulceration, etc. I believe people who have been vaccinated have experienced it. Some vaccines rarely cause adverse reactions, or the reactions are too mild to be detected. When the immune response of the vaccine subsides, the specific antibody corresponding to this vaccine will remain in the human body for a long time, while another kind of immune cells with memory function will record the pathogenic information. When the human body encounters the same pathogen again, the existing corresponding antibodies are immediately mobilized to deal with the "enemy", and the memory immune cells quickly call out the "files" of these "enemies" and immediately organize an effective defense response. Therefore, these pathogens were controlled by the human body's defense system before the disturbance, and the disease was naturally prevented.

Vaccines can be divided into live attenuated vaccines and inactivated vaccines according to different preparation processes. Live attenuated vaccines are prepared from non-toxic or less virulent strains or virus strains, such as measles vaccine. After vaccination, the attenuated strain survives and reproduces in the body, thus stimulating the body to produce an immune response, which is equivalent to a natural infection process. This kind of vaccine has good immune effect, and the vaccination dose is relatively small. Inactivated vaccine uses artificial methods such as heating to kill pathogens, but retains its original characteristics that can cause immune response. It can also cause immune response after vaccination, so as to protect the body. With the continuous development and progress of Biochemistry, molecular biology and bioengineering technology, new vaccines are emerging, such as multivalent vaccine and DNA gene vaccine. Polyvalent vaccine is composed of several vaccines or a mixture of vaccines and toxoids in a certain proportion. One injection can prevent many diseases at the same time, such as DPT vaccine, leprosy mumps vaccine, etc. Gene vaccine is a vaccine prepared by DNA recombination technology, which directly integrates the DNA of the pathogen into a suitable carrier and inoculates the human body, so as to stimulate the immune response of the human body.

Vaccination is often called vaccination, because injection is a common method of vaccination. But in fact, the ways of vaccination include oral administration, aerosol inhalation and scratches. Different vaccination routes are different. If the vaccination route is improper, it will not only affect the immune effect, but also may lead to adverse reactions.

After vaccination, in addition to activating the body to produce corresponding antibodies to protect its own health, sometimes it may also have adverse effects on the body or cause allergic reactions due to the quality of the vaccine itself, which we call side effects of vaccination. Common side effects of vaccination include general reactions and abnormal reactions. General reactions are local or systemic allergic reactions caused by the characteristics of biological products, such as local swelling, fever, nausea, vomiting, etc; Abnormal reaction refers to the reaction requiring medical treatment and treatment after vaccination.

In order to prevent the occurrence of abnormal reactions, the World Health Organization (who) has made regulations on the immunization of certain populations or situations: Patients with abnormal immune function (such as immune deficiency and malignant diseases) cannot use live vaccines; Patients who are being treated with immune agents should not be vaccinated with live vaccines; Children with fever and other obvious symptoms of general discomfort need to delay vaccination; For vaccines requiring continuous multiple doses, if allergies or other serious adverse reactions occur during the previous vaccination, the vaccination of other doses should be cancelled; People with allergic constitution should use vaccines with caution.