Different Methods of vaccination

Intracutaneous, subcutaneous and intramuscular methods of administering vaccines

The main gateway to infection and natural immunization of the body are the skin, the mucosa of the respiratory tract and the gastrointestinal tract. Immunity to any causative agent of infectious diseases can be obtained practically with any method of vaccination. When choosing the method of vaccine introduction, factors such as its safety, effectiveness, economy, productivity, ease of use of the vaccine and the psychological factor (absence of discomfort and pain in the patient) are taken into account.

Parenteral methods of vaccination include all methods of antigen administration, bypassing the gastrointestinal tract (cutaneous, intradermal, subcutaneous, intramuscular, aerosol). Methods with violation of the integrity of the skin were called destructive or percutaneous methods. The immunization process begins at the sites of injection of the antigen, which is phagocytized and processed by auxiliary cells (macrophages, dendritic cells, etc.), and then appears as lymphocytes. The antigen and cells primed with antigen can penetrate through the lymph vessels into the thoracic duct, and from there into the blood. They can settle in other lymphoid and non-lymphoid organs, ensuring the development of general immunity.

Most vaccines are administered subcutaneously and sorbed preparations are administered intramuscularly. With these methods of vaccination, favorable conditions are created for creating a depot and penetrating the antigen into regional and distant lymph nodes. The volume of the vaccine for intramuscular injection can exceed 2-3 times the amount of vaccine administered subcutaneously.

Intramuscular administration of vaccines (upper outer quadrant of the gluteus muscle, the anterior-external area of the thigh) is the main way of immunization with sorbed preparations. In this case, the local reaction is weakly expressed. In patients with hemophilia, due to the possibility of bleeding, a subcutaneous method of administering vaccines should be used.

Subcutaneous vaccination is usually used for non-absorbed vaccines. The vaccine is injected into the scapular region or to the area of the outer surface of the shoulder at the level of the upper and middle third of the shoulder. Reactions to the vaccine with subcutaneous injection under the scapula are less pronounced compared with subcutaneous injection into other parts of the body. Soluble vaccines are stored in the subcutaneous tissue for up to 5 days, and sorbed preparations – up to 1 month or more.

Despite the widespread use of subcutaneous and intramuscular methods, they have a number of shortcomings: the possibility of violation of aseptic rules, the need for disposable syringes, low productivity,

The intradermal route is used to administer the BCG vaccine. The vaccine is injected into the area of the outer surface of the shoulder. This method requires a certain skill, the vaccine is injected under pressure until the appearance of “lemon crust”. If the BCG vaccine is incorrectly administered, there is a risk of a cold abscess.

The cumulative vaccination method

The cumulative vaccination method, widely used at the time for the prevention of smallpox, is used mainly for immunization with live vaccines against especially dangerous infections (plague, tularemia, anthrax, brucellosis, fever Ku). The cramping method allows to maximally decrease the reactogenicity of the vaccine, however, the non-standard dosage of the preparation and the scarification technique, as well as low productivity, limit the scope of this method.

Bezigolny method of vaccination

In the 1950s, a new method of vaccination appeared in the practice of public health: needle – free . The method is used for mass immunization of the population. The advantage of this method is high productivity, reduced risk of infection transmission, economy, lack of pain and discomfort when injected. Disadvantages: the possibility of the appearance of pinpoint bleeding, more pronounced reactions to the introduction of sorbed preparations due to their delay in the upper layers of the skin. The frequency of local and general reactions with such administration of drugs does not exceed the frequency of reactions when the vaccine is injected with a syringe.

Injectors are manufactured in various designs, adapted for mass vaccination companies (1000-1500 injections per hour) or for vaccination of limited groups of people (50-100 injections per hour). Injectors are constantly being improved in order to increase the reliability, accuracy and convenience of vaccination. However, the use of a needleless injector does not completely exclude the possibility of transmission of injections. We widely use the needleless injector BI-3M with the protector of anti-infective PPN-2doO, 5cm3.

Aerosol vaccination method

Vaccination methods that do not violate human natural barriers are devoid of many disadvantages of subcutaneous and intramuscular methods of administering vaccines. The problem of vaccination with the aerosol method began to be intensively developed after the publication of the works of AM Bezredki (1925), who advanced the theory of local immunity and believed that vaccines should be administered in the same way that pathogens infectious diseases enter the body.

Local immunity should be considered in the context of general immunity, local immunity can not provide a sufficient degree of protection of the body from infections. For such protection, the formation of general resistance is necessary, although the role of local immunity in this resistance can be significant.

Aerosol (inhalation) immunization occurs when vaccines are administered in the form of aerosols, although instillation of the vaccine into the nose is also accompanied by the penetration of the vaccine particles into the respiratory tract. For scientific purposes, sometimes used conjunctival method, in which the antigen quickly enters the nasal cavity and with the current of air – into the lungs. When nasal or chemical vaccines are introduced into the nose, concentrated vaccines must be used. The intranasal method is used primarily for the purpose of revaccination.

The mucosa of the respiratory tract in the upper parts is covered by a multilayer cylindrical ciliated epithelium, in the lower parts – by a two-layered, single-layered cylindrical, and then cubic ciliated epithelium. The bronchioles are lined with flat cells devoid of cilia. The total surface area of respiratory lungs is about 100 m2. In the interalveolar septa are leukocytes and septal cells that have phagocytic properties and the ability to penetrate into the alveoli, turning into alveolar macrophages.

In addition to alveolar macrophages, the immune system of the lungs is represented by cells of the interstitial, connective tissue, broncho-associated lymphoid formations and numerous regional lymph nodes. Macrophages and dendritic cells of broncho-associated formations cleave the introduced antigen and represent the formed peptides in complex with histocompatibility antigens to lymphocytes. Auxiliary cells that have come into contact with the antigen can migrate to the lymph nodes where they continue to perform antigen presenting function. The free antigen is absorbed through the lymphoid system into the general circulation of blood and, settling in the organs, triggers the immunization process. With aerosol vaccination, humoral and cellular immunity develops. In the secrets of the mucosa, immunoglobulin of various classes is detected, primarily secretory IgA, which is of local origin.

The particle size of the vaccine administered by the aerosol is essential for the development of immunity. The antigen acts throughout the entire airway, although highly disperse vaccines have stronger immunogenic properties. The bulk of the vaccine settles in the airways, only particles of no more than 10 µm in diameter penetrate the alveoli. It should be noted that as the dispersion of aerosol vaccines increases, their reactogenicity increases.

When the vaccines are aerosolized, mechanical protection mechanisms start to act that prevent the entry of foreign material into the lungs: accelerated settling of particles on the surface of the mucosa, the action of a ciliated epithelium, expelling vaccine particles along with mucus, sneezing, etc. Along with mechanical cleaning of the lungs, the introduced material and its enzymatic cleavage.

Aerosol vaccination allows to achieve increased lung resistance in a short time, which is of great importance for the prevention of respiratory infections. The aerosol vaccine falls not only into the lungs, but also partially into the gastrointestinal tract, this increases the tension of developing immunity.

The effectiveness of aerosol immunization is not inferior to other methods of antigen administration , and in some cases even exceeds them. It is noteworthy that the level of sensitization of the body, achieved by aerosol vaccination, does not exceed the degree of hypersensitivity in other methods of immunization. Postvaccinal reactions develop shortly after inhalation or after 3-6 days and are predominantly general in nature (fever, headache, general weakness, pain in muscles and joints, nausea, loss of appetite).

With aerosol immunization, an immune response can be obtained to any vaccine (live, dead, chemical, liquid, dry). More convenient are dry concentrated vaccines with a certain fractionally dispersed composition. For some vaccines, a filler is necessary, which helps to disperse vaccines when sprayed.

Disadvantages of aerosol vaccination

Disadvantages of aerosol vaccination are a small percentage of digestible vaccine assimilability in a group vaccination method, the complexity of vaccine manufacturing technology, the use of excipients, stabilizing additives, the need for special equipment and devices for spraying vaccines for their individual or group use.

In the practice of health, complex aerosol formulations are used, which include antigens of pathogens, obligatory living in the upper respiratory tract of a person, for the prevention and treatment of chronic lung infections.

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