Childhood diseases. Vaccination (lecture notes)

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Childhood diseases. Vaccination (lecture notes)

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LECTURE No. 5. Vaccination

The organization of preventive work among the child population includes, first of all, vaccination (that is, specific immunization), as well as a system of measures aimed at early detection of the disease and dispensary observation of sick and recovered children. Preventive vaccinations are the most important means of specific immunoprophylaxis and effective control of many infectious diseases. Thanks to the widespread introduction of vaccination in the world, smallpox was completely eliminated, and the number of cases of tetanus, whooping cough, and measles decreased tenfold.

What is vaccination? This is the creation in the human body of protection against the causative agent of infection. This method has been known for several hundred years. Unfortunately, at present there are no vaccines for all infectious agents, but these methods of protection have been created and successfully applied to many of them - against tuberculosis, hepatitis, whooping cough, diphtheria, tetanus, rabies, poliomyelitis, rubella, chicken pox, mumps , measles, etc. In the process of vaccination, specific immunity to infection is created by simulating the infectious process. For this, various types of vaccines are used. In addition, immunity is acquired after the transfer of an infectious disease. As well as after vaccination, and after illness, immunity can be lifelong, persistent or persist for a certain time.

1. Live vaccines

They consist of living but weakened (attenuated) pathogens. Virus strains are taken as pathogens. Examples of live vaccines: rubella, influenza, polio Sabin, mumps. They contain viruses that, when they enter the human body, cause the production of all parts of the immune response (cellular, humoral, secretory). When using live vaccines, stable, intense, long-term immunity is created, but there are a number of disadvantages:

1) a weakened vaccine virus can acquire virulence, i.e., become the causative agent of the disease (for example, vaccine-associated poliomyelitis);

2) live vaccines are difficult to combine, as this can mix viruses and the vaccine may become ineffective;

3) live vaccines have thermolability, i.e., they can lose their properties when the storage temperature changes. Live vaccines also include vaccines containing cross-reacting components that cause a weakened infection in the human body, protecting it from a more severe one. An example of such a vaccine is BCG containing bovine tuberculosis microbacteria;

4) live vaccines have a number of contraindications: they cannot be administered to patients with immunodeficiency; patients using steroid hormones, immunomodulators (suppressors); people who have undergone radiotherapy; patients with blood diseases (with leukemia), tumors of the lymphoid tissue (lymphomas), as well as pregnant women.

2. Killed vaccines

They contain dead pathogens, are easily dosed and combined with other vaccines, and are thermally stable. Killed vaccines cause the production of several types of antibodies that enhance the phagocytosis of microorganisms. An example is the pertussis vaccine. It also has an adjuvant effect, enhancing the immune response to another antigen that is part of the combined (associated) vaccine - DTP.

Disadvantage: when using these vaccines, only a humoral unstable link of immunity arises, therefore they act only for a certain time, require administration in several doses and re-vaccination throughout life. They are often administered with an adjuvant (an adjuvant that enhances the immune response) which is an aluminum compound. The adjuvant acts as a reservoir in which the antigen is stored for a long time. All killed vaccines also contain a preservative (an organic compound of mercury in an amount safe for humans).

3. Recombinant vaccines and toxoids

An example of such a vaccine is the vaccine against viral hepatitis B. In its preparation, a subunit of the virus gene is inserted into yeast cells. The yeast is then cultured and HBsAg is isolated from them. It is cleaned of yeast inclusions. This method of preparing a vaccine is called recombinant. This vaccine also contains a preservative and adsorbent in the form of aluminum hydroxide.

Toxoids are substances produced by pathogens. When preparing a number of vaccines, it is impossible to use the pathogen itself, therefore, in these cases, their toxin is taken. These are tetanus, diphtheria, staphylococcal and some other toxins.

Anatoxins cause persistent antitoxic immunity, they are easy to combine and dose. They are obtained by treating the toxin with formaldehyde under special temperature conditions. In this case, the toxin is neutralized, but its immune properties are preserved. The immunity produced by toxoids is only antitoxic. When using toxoids, bacteriocarrier and the occurrence of mild forms of the disease are possible.

4. Formation of an immune response

An important feature of children of the first year of life is that they have innate immunity to certain infectious diseases. The origin of this immunity is transplacental. Class G immunoglobulins cross the placenta from the 16th week of pregnancy. Thus, the fetus begins to receive ready-made maternal antibodies, and passive individual immunity is formed even in the prenatal period. Passive immunity is called immunity, in which the body acquires ready-made antibodies, and does not produce them itself during vaccination or the transfer of an infectious disease. After the birth of a child, individual maternal antibodies begin to break down, starting at 2 months of age. By the end of the first year of life, they completely disappear. Thus, the body of a newborn during the first year of life is protected from those infections, antibodies to which were obtained from the mother. These antibodies can interfere with vaccine immunity, and this factor is taken into account when developing a vaccination schedule.

Features of the immune response in the human body to the penetration of the antigen determines the main system of histocompatibility. It is located on chromosome 6 and is designated HLA. HLA are antigens found on peripheral blood leukocytes. The height of the immune response, the level of suppression of the formation of antibodies depends on them. Various cells are involved in the immune response: these are macrophages, T-lymphocytes (effector, helper, suppressor, memory T-cells). Also involved in this complex process are B-lymphocytes (memory B-cells), immunoglobulins of classes M, G, A, produced by plasma cells, cytokines. The components of the injected vaccine are taken up by macrophages, which cleave the antigen inside the cell and present parts of the antigen on their surface. T-lymphocytes recognize them and activate B-lymphocytes. B-lymphocytes become cells that form antibodies.

The primary administration of the vaccine takes place in 3 periods:

1) latent - this is the time between the introduction of the antigen and the appearance of antibodies in the blood. It can last from several days to 2-3 weeks depending on the type of vaccine, dose, and the state of the child’s immune system;

2) growth period - at this time, the number of antibodies increases rapidly. This period lasts from 4 days to 3 weeks (depending on the type of vaccine). The amount of antibodies increases especially rapidly with the introduction of measles and mumps vaccines, which makes it possible to use them for active immunization during emergency prophylaxis. With the introduction of pertussis and diphtheria components of DPT, the level of antibodies increases much more slowly than during the incubation period of the onset of the disease, therefore DTP is not used for emergency prevention;

3) a period of decline. After reaching the maximum level in the blood, the amount of antibodies begins to decrease rapidly, then the process slows down. It can go on for years or decades.

5. Immunization calendar and rules for the introduction of vaccines for certain types of vaccinations

BCG vaccination

Vaccination of newborns is carried out on days 4 - 7 of life directly in the ward after examination by a pediatrician. The anti-tuberculosis vaccine is live mycobacteria dried in a solution of monosodium glutamate. It is available in ampoules containing 1 mg of BCG, which is 20 doses of 0,05 mg of the drug. To obtain the required dose of 0,05 mg of BCG in 0,1 ml of solution, the dry BCG vaccine is diluted in 2 ml of isotonic sodium chloride solution. The vaccine is used no later than 2-3 hours after dilution. The newborn's history indicates the date of vaccination and the vaccine series. The exchange card sent to the children's clinic indicates the date of intradermal vaccination, the series of the vaccine, its expiration date, control number and the name of the manufacturing institute.

The BCG vaccine is administered at the border of the upper and middle third of the outer surface of the left shoulder after pre-treatment of the skin with a 70% solution of ethyl alcohol. The vaccine is administered strictly intradermally in a volume of 0,1 ml. At the injection site, a whitish papule is formed, 6 - 8 mm in diameter. After 15-20 minutes, the papule disappears and the skin acquires a normal color. The injection site should not be treated with disinfectant solutions, and a bandage should not be applied. In those vaccinated during the neonatal period, at the site of intradermal administration of the BCG vaccine, after 6 - 8 weeks, a specific reaction develops in the form of an infiltrate with a diameter of 5-10 mm with a small nodule in the center and the formation of a crust. Reversal of changes at the grafting site occurs within 2-4 months, after which a scar measuring up to 10 mm remains.

A gentle immunization with the BCG-M vaccine preparation has also been introduced, which is used in premature babies, as well as in newborns with purulent-septic diseases, hemolytic disease of the newborn, severe birth injuries, and generalized skin diseases.

Anti-tuberculosis revaccination is carried out in children's polyclinics, outpatient clinics under the guidance of an anti-tuberculosis dispensary. Re-vaccination of children in the absence of a scar can be carried out only according to epidemiological indications with a negative Mantoux test 2TE, not earlier than 2 years after the primary revaccination. This is usually done at the age of 7 years.

Contraindications to BCG revaccination: past tuberculosis, positive or doubtful Mantoux tests with 2TE PPD-L, complicated reactions to the previous administration of BCG (keloid scars, chronic diseases in the acute stage, allergic diseases in the acute stage, malignant neoplasms and blood diseases, immunodeficiency states).

Complications after BCG vaccinations are usually rare. They are expressed in the form of lymphadenitis, keloid scars and cold abscesses.

DTP vaccination

It is carried out with a DPT-vaccine - a mixture of purified concentrated diphtheria and tetanus toxoids adsorbed on aluminum oxide hydrate, as well as pertussis vaccine. The first vaccination is carried out at 3 months. Vaccination 3 times. The second - at 4,5 months, the third - at 6 months. The first revaccination is carried out at the age of 18 months. The second - in 7 years.

The vaccination dose is 0,5 ml, administered intramuscularly. The vaccine is highly effective, but can cause a general reaction in the form of fever, sleep disturbance, appetite, and allergic reactions. Children prone to allergic manifestations (exudative diathesis, asthmatic bronchitis, bronchial asthma, neurodermatitis) are vaccinated with ADS vaccine without a pertussis component.

Polio vaccination

An oral live polio vaccine is used, which is a mixture of attenuated Sabin strains of the 1st, 2nd, 3rd types, cultivated on a primary culture of green monkey kidney cells. Produced in liquid form in 5 ml bottles and in the form of dragees. Dragees with a mixture of 3 immunological types are white, type 1 - pink, type 2 - lilac, type 3 - blue. Each tablet contains one vaccination dose. Liquid polio vaccine is available as a monovaccine and a trivaccine. The grafting dose of liquid monovaccine is contained in 2 drops (0,1 ml), trivaccine - in 4 drops (0,2 ml). To prevent paralytic poliomyelitis, 5 injections of the vaccine are needed.

Specific prophylaxis against polio for all children is carried out from the age of 3 months three times with an interval of 1,5 months. Revaccination is carried out at 1-2 and 2-3 years twice with an interval of 1,5 months and once at 6-7 years and at 14 years. The vaccine has virtually no adverse reactions and can be combined with the DTP vaccine.

Rubella vaccination

The rubella vaccine is a live lyophilized attenuated vaccine that also contains neomycin. It is produced in the form of a monovaccine and a divaccine (mumps-rubella). It is recommended to vaccinate girls of pubertal age and women of childbearing age who do not plan pregnancy in the next few months.

Mumps vaccination

Mumps vaccine is a live, attenuated, contains antibiotics of the aminoglycoside group. Children from 12 months to 7 years of age who have not previously been ill are vaccinated. Vaccination is mandatory for boys, since one of the complications after mumps may be orchitis and subsequently infertility. The vaccine is administered subcutaneously, under the shoulder blade or in the shoulder area. Immunity is maintained for 8 years.

Measles prevention provides for the introduction of measles vaccine to all children at 12 months and 7 years, and from 1990 to those who do not have measles antibodies.

Vaccination against viral hepatitis B.

Specific prophylaxis has been carried out since 2001 for all newborns in the first 12 hours after birth, then one month and 6 months after the first administration of the drug. The recombinant vaccine "KOMBITEKS" is used

For children whose mothers are carriers of viral hepatitis B or have had it in the last trimester of pregnancy, the vaccine is administered according to the following scheme: 0-1-2-12. In view of the fact that in recent years the incidence of viral hepatitis B among adolescents has increased, it is advisable to vaccinate children aged 8-11 years according to the scheme: 2 vaccinations at a monthly interval and subsequent administration after 6 months.

Показания for vaccinations:

1) scheduled vaccinations for children according to the calendar and military personnel;

2) unscheduled vaccinations in case of a threat of an occupational disease, residence and upcoming trip to the epidemiological territory, emergency vaccination of persons in contact with the source of infection.

Противопоказания for vaccinations:

1) severe reaction (fever, swelling at the site of the vaccine, hyperemia during the first or repeated administration);

2) complications during the first or repeated administration;

3) immunosuppression;

4) immunodeficiency state;

5) malignant blood diseases, neoplasms;

6) progressive diseases of the nervous system;

7) pregnancy;

8) allergic reactions, anaphylactic shock.

Author: Gavrilova N.V.

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