Despite the important contribution of vaccination to reducing the incidence of influenza, the prevalence of this infection remains extremely high. Influenza is the leading cause of seeking medical care for acute respiratory infections, causing up to 300,000 hospitalizations and leading to 20 to 40,000 deaths per year.

The highest risk of infection, the development of complications and the side effects of the infection are children, the elderly and people with chronic comorbidity. So in 2002-2003. the frequency of hospitalization of children under 5 for influenza was 0.9 per 1000. In contrast, more than 90% of deaths from influenza and related complications were noted in people over the age of 65 years.

Seasonal flu epidemics are caused by two types of viruses - A and B, while type C causes sporadic infections. Influenza A and B viruses are constantly undergoing changes in the surface antigens - hemagglutinin (H) and neuraminidase (N), which are considered to be evolutionary adaptability and make it difficult for them to be recognized and eliminated by the system. human immune system. There are two mechanisms of antigenic variation: 1) antigenic drift, leading to relatively small changes, and 2) antigenic shift, leading to pronounced changes (occurs every 10 to 40 years).

The great variability of the influenza virus requires the regular development of new vaccines. Each year, under the auspices of WHO, viral strains are determined with the highest probability of circulation during the coming season, and the development of vaccines from them, taking into account variations antigenic. The vaccine includes 3 types of viral antigens - 2 types A and 1 type B. The process of development and release of vaccines takes approximately 6 months and, for many reasons, this method is problematic (complexity of the development process, time production, potential contamination of chicken embryos by bacteria, on which virus culture, etc.) is carried out.

The whole virion inactivated trivalent vaccine was introduced into clinical practice in the 1950s and contained dead whole virus particles. Currently, a trivalent subunit vaccine is used, consisting of purified subunits of neuraminidase antigens and viral hemagglutinin antigens.

The antibodies produced by intramuscular administration of the vaccine inhibit replication of the virus, but do not provide adequate secretory immunity, which minimizes the risk of infection. The protective reaction after the introduction of the vaccine has been shown to be directly proportional to the recipient's immune response, however, in the elderly, this dependence is not always detected. It should also be borne in mind that the vaccine is effective only against viral strains containing similar H and N antigens.

The vaccines currently in use are thoroughly cleaned, do not contain live virus particles and cannot lead to influenza infection. The side effects that develop after their administration occur relatively rarely and, as a rule, of mild severity.

According to the recommendations of the Centers for Disease Control and Prevention (CDC, USA), the optimal time for vaccination is from October to November until a seasonal peak of incidence occurs. At the same time, the Advisory Committee on Immunization Practices (ACIP) notes the possibility of administering the vaccine throughout the epidemic season, since the concentration of influenza antibodies becomes protective several weeks after the introduction of the vaccine and the epidemic season can last much longer.

The vaccine is administered once a year at a dose of 0.5 ml in the deltoid muscle in adults and children over 3 years of age. Children aged 6 to 35 months receive 0.25 ml of vaccine intramuscularly into the anterolateral thigh. Influenza vaccination can be carried out simultaneously with the introduction of other vaccines, for example with pneumococcal conjugate vaccine, provided that they are administered in different anatomical areas in different syringes.

If the viruses contained in the vaccine correspond to circulating epidemic strains, the reduction in the frequency of hospitalization and mortality from influenza during its use reaches 70 to 90% in relatively healthy adults, as well as in children and teens.

Analysis of the feasibility of vaccination costs for healthy adults confirmed the positive effect on the population level of vaccination of all people aged 18 to 50 years. In a placebo-controlled study of 849 healthy people aged 18 to 64, it was shown that administration of a trivalent influenza vaccine was reduced by 25% in the number of visits to a doctor for upper respiratory tract infections, 43% for days of disability and $ 46. , 85 on 1 vaccinated person.

In the elderly, vaccine prophylaxis has reduced the frequency of hospitalizations for influenza by 50 to 60% and reduced mortality by 80%. The lower vaccine efficacy of the elderly may be due to concomitant chronic pathology and age-related changes in the immune system. Nevertheless, according to research results, vaccination of this category of people is clinically and economically feasible.

Earlier, it was suggested that the annual introduction of the vaccine may become addictive over time and lead to a decrease in protective immunity, but studies have not confirmed this hypothesis. There was also no significant association between the use of the trivalent vaccine and the development of Guillain-Barré syndrome (acute demyelinating polyneuropathy) (frequency less than 1 in 1 million vaccinated). At the same time, the previously transferred Guillain-Barré syndrome is a contraindication to vaccination.

In a number of cases, the development of anaphylactic-type allergic reactions to chicken protein and thimerosal preservative has been noted, however, the introduction of vaccines for allergy sufferers is considered possible after specific desensitization.

The goal of vaccination is to prevent seasonal flu epidemics. According to CDC recommendations, the indications for vaccination are:

The frequency of vaccination of medical personnel against influenza is not yet sufficiently high. Thus, at present, only 40% of medical workers in the United States undergo an annual vaccination, although it has been recommended since 1981. In USA, this indicator is even lower.

At the same time, during the epidemic season, medical workers often come into contact with patients with the acute phase of the flu, which greatly increases the risk of infection with subsequent transmission of the infection to others. patients and, in turn, leads to an increase in the length of hospital stay of patients and the frequency of exacerbation of concomitant treatments. diseases and mortality.

Currently, vaccination of medical personnel is seen as one aspect of improving the safety and quality of medical care, which has led to the implementation of a universal vaccination strategy for medical personnel in 22 American states.

Despite preventive and therapeutic measures, the flu still contributes significantly to infectious morbidity and mortality. The introduction of a universal influenza vaccination strategy supported by a number of US regulators can have a marked positive effect on the state of this problem.