What is a vaccine? Types and types of vaccines
Over the centuries, mankind has experienced more than one epidemic that claimed the lives of many millions of people. Thanks to modern medicine, it was possible to develop drugs that allow to avoid many deadly diseases. These drugs are called "vaccine" and are divided into several types, which we describe in this article.
What is a vaccine and how does it work?
A vaccine is a medical product containing killed or weakened pathogens of various diseases or synthesized proteins of pathogenic microorganisms. They are introduced into the human body to create immunity to a particular disease.
The introduction of vaccines into the human body is called vaccination, or vaccination. The vaccine, entering the body, causes the human immune system to produce special substances for the destruction of the pathogen, thereby forming his selective memory of the disease. Subsequently, if a person is infected with this disease, his immune system will quickly counter the pathogen and the person will not get sick at all or will suffer a mild form of the disease.
Immunobiological preparations can be administered in various ways according to the instructions for vaccines, depending on the type of drug. There are the following methods of vaccination.
- The introduction of the vaccine intramuscularly. The vaccination site in children under one year old is the upper surface of the mid-thigh, and for children from 2 years old and adults it is preferable to inject the drug into the deltoid muscle, which is located in the upper part of the shoulder. The method is applicable when an inactivated vaccine is needed: DTP, ADS, against viral hepatitis B and anti-influenza vaccine.
Feedback from parents suggests that infants tolerate vaccination better in the upper thigh than in the buttock. Doctors also adhere to this opinion, provoking this by the fact that in the gluteal region there may be abnormal placement of nerves, found in 5% of children under one year of age. Moreover, in the gluteal region, children of this age have a significant fatty layer, which increases the likelihood of the vaccine entering the subcutaneous layer, which reduces the effectiveness of the drug.
- The intranasal method is applicable to vaccines in the form of an ointment, cream or spray (measles, rubella vaccine).
- The oral route is when a vaccine in the form of drops is placed in the patient’s mouth (polio).
Types of vaccines
Today in the hands of medical workers in the fight against dozens of infectious diseases there are more than a hundred vaccines, thanks to which we managed to avoid whole epidemics and significantly improve the quality of medicine. It is conditionally accepted to allocate 4 types of immunobiological preparations:
- Live vaccine (polio, rubella, measles, mumps, influenza, tuberculosis, plague, anthrax).
- Inactivated vaccine (against pertussis, encephalitis, cholera, meningococcal infection, rabies, typhoid fever, hepatitis A).
- Anatoxins (tetanus and diphtheria vaccines).
- Molecular or biosynthetic vaccines (for hepatitis B).
Types of vaccines
Vaccines can also be grouped on the basis of the composition and method of their production:
- Corpuscular, that is, consisting of whole pathogen microorganisms.
- Component or cell-free consists of parts of the pathogen, the so-called antigen.
- Recombinant: the composition of this group of vaccines includes antigens of the pathogenic microorganism, introduced using the methods of genetic engineering into the cells of another microorganism. A representative of this group is the flu vaccine.Another vivid example is the vaccine against viral hepatitis B, which is obtained by introducing antigen (HBsAg) into yeast fungus cells.
Another criterion by which a vaccine is classified is the number of diseases or pathogens it prohibits:
- Monovalent vaccines serve to prevent only one disease (for example, the BCG vaccine against tuberculosis).
- Polyvalent or associated - for vaccination against several diseases (for example, DTP against diphtheria, tetanus and whooping cough).
Live vaccine is an indispensable drug for the prevention of many infectious diseases, which is found only in the particulate form. A characteristic feature of this type of vaccine is that its main component is weakened strains of the infectious agent that can multiply, but are genetically deprived of virulence (ability to infect the body). They promote the body's production of antibodies and immune memory.
The advantage of live vaccines is that even live, but weakened pathogens induce the human body to develop a long-term immunity to the pathogenic agent, even with a single vaccination.There are several ways to administer the vaccine: intramuscularly, under the skin, nasal drops.
The disadvantage is that a gene mutation of pathogenic agents is possible, which will lead to the graft disease. In this regard, contraindicated for patients with particularly weakened immunity, namely for people with immunodeficiency and cancer patients. Requires special conditions of transportation and storage of the drug in order to ensure the safety of living microorganisms in it.
The use of vaccines with inactivated (dead) pathogenic agents is widespread for the prevention of viral diseases. The principle of action is based on the introduction into the human body of artificially cultivated and viral pathogens deprived of viability.
“Killed” vaccines can be either whole microbial (whole-helical) or subunit (component) or genetically engineered (recombinant) vaccines.
An important advantage of the "dead" vaccines is their absolute safety, that is, the absence of the likelihood of infection of the vaccinated and the development of infection.
The disadvantage is the lower duration of immune memory compared to “live”vaccinations, as well as inactivated vaccines, the likelihood of the development of autoimmune and toxic complications remains, and for the formation of a complete immunization several procedures of vaccination are required with maintaining the necessary interval between them.
Anatoxins are vaccines created on the basis of disinfected toxins released during the life of some pathogens of infectious diseases. The peculiarity of this vaccination is that it provokes the formation of not microbial immunity, but of antitoxic immunity. Thus, toxoids are successfully used to prevent those diseases in which the clinical symptoms are associated with a toxic effect (intoxication) resulting from the biological activity of the pathogenic pathogen.
The release form is a clear liquid with sediment in glass ampoules. Before use, shake the contents to evenly distribute toxoids.
The advantages of toxoids are indispensable for the prevention of those diseases against which live vaccines are powerless, moreover, they are more resistant to temperature fluctuations, do not require special storage conditions.
Disadvantages of toxoids - induce only antitoxic immunity, which does not exclude the possibility of localized diseases in the vaccinated, as well as the carriage of pathogens of this disease.
Production of live vaccines
Mass vaccines began to be produced at the beginning of the 20th century, when biologists learned how to attenuate viruses and pathogens. Live vaccine is about half of all prophylactic drugs used by world medicine.
The production of live vaccines is based on the principle of reseeding a pathogen into an immune or low-susceptible organism (virus) organism or cultivating the pathogen under adverse conditions with physical, chemical and biological factors, followed by the selection of non-virulent strains. The most common substratum for the cultivation of avirulent strains are chicken embryos, primary cell (chicken erythral fibroblasts or quail) and transplanted cultures.
Getting "killed" vaccines
The production of inactivated vaccines from live ones is different in that they are produced by killing, and not by attenuating the pathogen.To do this, only those pathogenic microorganisms and viruses that possess the greatest virulence are selected, they must be the same population with clearly defined characteristics characteristic of it: shape, pigmentation, size, etc.
Inactivation of pathogen colonies is carried out in several ways:
- overheating, that is, exposure of the cultured microorganism to elevated temperature (56-60 degrees) for a certain time (from 12 minutes to 2 hours);
- exposure to formalin for 28-30 days with maintaining the temperature at 40 degrees, a solution of beta-propiolactone, alcohol, acetone, chloroform can also act as an inactivating chemical reagent.
In order to obtain toxoids, toxogenic microorganisms are first cultivated in a nutrient medium, most often of a liquid consistency. This is done in order to accumulate as much exotoxin in the culture. The next stage is the separation of the exotoxin from the producer cell and its neutralization using the same chemical reactions that are used for “killed” vaccines: exposure to chemical reagents and overheating.
To reduce the reagent and susceptibility, antigens are cleared of ballast, concentrated and adsorbed with aluminum oxide. The process of adsorption of antigens plays an important role, since the injection injected with a high concentration of toxoids forms a depot of antigens, as a result, the antigens enter and spread throughout the body slowly, thus ensuring an effective immunization process.
Destruction of unused vaccine
Regardless of which vaccines were used for vaccination, containers with residual preparations must be processed in one of the following ways:
- boiling used containers and tools for an hour;
- disinfection in a solution of 3-5% chloramine for 60 minutes;
- treatment with 6% hydrogen peroxide also for 1 hour.
Preparations with an expired shelf life should always be sent to the district sanitary epidemiological center for disposal.