Knowledge About Vaccines

Knowledge About Vaccines. Vaccines are the most economical, effective, safest and most convenient scientific and technological invention for mankind to overcome major infectious diseases. Vaccination is the most cost-effective public health intervention to prevent and control infectious diseases.

Since humans have mastered the principles and technology of vaccines, smallpox has been eliminated, measles, and polio have been eliminated worldwide, and the epidemic of pertussis, diphtheria, hepatitis A and other diseases have been effectively controlled. The current vaccine can prevent 2 million to 3 million annually Of deaths.
Today I will lead you to talk about the truth about vaccines.

Definition of vaccine

As the name implies, everyone knows that vaccines are organisms that are used to prevent and treat diseases using traditional methods or genetic engineering techniques to obtain microbial proteins, polysaccharides, nucleic acids and other immunogenic biological materials (in vivo induction, active immunity) that are used to prevent and treat diseases. Products.
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Vaccines can be monovalent or multivalent. A monovalent vaccine is a single strain containing a single antigen (such as measles vaccine), and a multivalent vaccine contains two or more strains/serotypes of the same antigen (such as influenza vaccine, HPV). Vaccine), the combination vaccine contains two or more antigens (such as DPT vaccine).
Note: There is no evidence that multiple antigens in the combined vaccine will increase the burden on the immune system and increase the probability of adverse reactions. The human immune system can simultaneously resist the immune response generated by millions of antigens. On the contrary, the combined vaccine reduces the occurrence of overall adverse reactions, so it is a good explanation for the impact of the epidemic. It is safe and reliable to vaccinate children with two or more vaccines at the same time.

Vaccine classification

For the general public, vaccines are divided into immunization program vaccines (free) and non-immunization program vaccines (other vaccines voluntarily vaccinated by citizens). Today we will talk about the classification according to the characteristics of vaccines. There are four types: live attenuated Vaccine, inactivated vaccine (dead antigen), subunit vaccine (pure antigen), toxoid vaccine (inactivated toxin compound).

1. Live attenuated vaccine

The toxins or bacteria are cultured for multiple generations to attenuate or weaken them, and retain the immunogenicity. The obtained vaccine microorganisms can increase in the recipients, thereby generating immunity, which usually does not lead to the occurrence of diseases, and natural infections. The immune response is almost the same.

• Advantages: The first dose of live attenuated vaccine usually produces protection, and the second dose can ensure seroconversion. For example, 95%-98% of the recipients can have an immune response after receiving the first dose of Japanese encephalitis vaccine , Nearly 100% of the recipients can get immunity after receiving the second dose (the second dose is “insurance”). The immunization time of live attenuated vaccine is long, and booster immunization is not necessary. The exception is the oral polio vaccine, which requires multiple doses.
• Disadvantages: Live attenuated vaccines are often unstable, resistant to heat, and light. They must be taken care of and transported carefully. Part of the toxicity may be restored when the immune system is weakened, which may lead to vaccine-related diseases.

Common vaccines: Leprosy, MMR, Japanese encephalitis attenuated, hepatitis A attenuated, chickenpox, oral polio vaccine, etc.

2. Inactivated vaccine

Use culture medium to cultivate viruses or bacteria, and then inactivate them with heat or chemical substances (mostly formalin). It will not replicate and increase in the recipient’s body. Therefore, immune-deficient people will not cause disease if they are inoculated. (Eg HIV-positive children).

• Advantages: safer, will not cause disease, often not affected by circulating antibodies, and more stable.
• Disadvantages: There are many inoculation doses, and more than 2-3 times are required. Generally speaking, the first dose only activates the immune system and usually does not produce immunity. Protective immunity will only develop after multiple doses. The duration of immunity is short. Therefore, some inactivated vaccines require regular supplementation. Times.

Common vaccines: IPV, EV71, hemorrhagic fever, inactivated Japanese encephalitis, inactivated hepatitis A vaccine, etc.
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3. Subunit vaccine

Use the culture medium to cultivate the whole pathogen, and then undergo further processing and purification to retain only certain components of the vaccine species (such as protein, bacterial capsular polysaccharide).

Protein vaccine:

A vaccine made by isolating and extracting immunogenic proteins from pathogens. For example, yeast hepatitis B vaccine inserts the hepatitis B virus gene into yeast cells. The modified yeast cells can produce a large amount of hepatitis B surface antigen, which is purified. Extracted and manufactured.

• Advantages: Stable and safe.
• Disadvantages: There are many inoculation doses, more than 2-3 doses are required.

Common vaccines:

yeast hepatitis B vaccine, whooping cough vaccine, etc.

Polysaccharide vaccine:

A vaccine made by isolating and extracting bacterial capsular polysaccharides from pathogens. It contains the polysaccharide coat or shell of capsular bacteria. It is a purified, non-infectious vaccine.

• Advantages: stable and safe.
• Disadvantages: The effect of vaccination is not good for children under two years of age, because the immune system of children under two years of age is not well developed and cannot produce a good immune response to the polysaccharide antigen produced by the T cell-independent mechanism.

Common vaccines:

Group A polysaccharide, Group A+C polysaccharide, 23-valent pneumonia vaccine, etc.

Combination vaccine:

Combination of polysaccharide and protein vaccine, combining the advantages of protein vaccine and polysaccharide vaccine, common group A+C group vaccine, AC group+HIB combination vaccine, etc.

Toxoid vaccine:

a vaccine made through the purification of toxins and chemical treatment (often formaldehyde). In some bacterial infections (such as diphtheria, tetanus), the clinical manifestations of the disease are not caused by the bacteria themselves, but by the toxins they secrete.
Advantages: Toxoid vaccines are no longer toxic, and vaccination is safe and reliable. Tetanus vaccines are common.

Other ingredients in the vaccines

Adjuvants: In the vaccine production process, adding some to enhance the strength and/or durability of the immune response to reduce the immunogen dose per dose, or to reduce the total doses of inoculation required for immunity. Common adjuvants such as aluminum hydroxide, aluminum phosphate, aluminum potassium sulfate, etc., mainly increase the immune response to protein.

• Antibiotics: To prevent the tissue culture cells for virus growth from being contaminated by bacteria, neomycin is added to common measles vaccine and IPV vaccine.
• Preservatives: Adding chemical substances (such as thimerosal) to inactivated vaccines or subunit vaccines to inactivate viruses, detoxify bacterial toxins, and prevent serious secondary infections caused by bacterial and fungal contamination.
• Stabilizer: Add chemicals to vaccines, such as freeze-dried vaccines. In order to stabilize the antigen and prevent the antigen from attaching to the surface of the ampoule, causing the loss of the immune prototype, aluminum salts, sodium salts, lactose, human serum proteins and various Kind of animal protein and so on.

Note: Other ingredients in the vaccine are removed in the subsequent production process, but very few of its ingredients may remain in the final product, which may have adverse effects on people who are allergic to the residue.

Phase IV clinical trials of vaccine development

• Phase I: Clinical pharmacology and human safety test to observe human metabolism and safety
• Phase II: Double-blind controlled human trial to observe effectiveness and safety
• Phase III: Multi-base clinical trials, expanded observation of effectiveness and safety
• Phase IV: monitor after application to observe the effectiveness and adverse reactions during widespread use

Today we learned about vaccines together. The development and production of a new vaccine to its widespread use is a complicated and long process. The application of vaccines not only reduces the incidence and mortality of infectious diseases, but also HPV vaccines and influenza vaccines. , Pneumonia vaccine, etc. can also directly or indirectly prevent some cancers and chronic diseases.

At the same time, the key to achieving excellent results of vaccination is the high vaccination rate. The high vaccination rate of the population can obtain the effect of herd immunity and reduce the spread of vaccines against diseases.

In recent years, with the impact of various vaccine incidents, the people have insufficient confidence in the safety of vaccines. I hope that through today’s study, everyone can have a new understanding of vaccines, understand the advantages and disadvantages of various vaccines, and be able to choose vaccines correctly. Effectively protect the health of children and adults and reduce medical expenses.

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