Prevention of hepatitis A

Prevention of hepatitis A is the same as with other intestinal infections. It is built taking into account the three links of the epidemic chain (the source of the infection, the route of its transmission and the receptive organism).

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Identifying the source of infection

The system of measures aimed at neutralizing the source of infection presupposes, first of all, early diagnosis of all cases of diseases and timely isolation of patients. It should be noted, however, that in the case of hepatitis A, the preventive value of these measures is ineffective. The reason is that the source of infection is not so much patients with typical, easily diagnosed icteric forms of the disease. How many patients with atypical, jaundiced, erased and subclinical forms of hepatitis A, diagnosis of which is very difficult or even impossible without the use of modern laboratory methods. No less important is the fact that the maximum contagiosity in hepatitis A occurs on the horses of the incubation period and the onset of the disease, when there are no manifest clinical symptoms of the disease.

It is obvious that the existing level of diagnosis of hepatitis A does not allow to effectively influence the first link of the epidemic process. Nevertheless, with the appearance of the first case of the disease, it is necessary to identify the source of infection, to conduct a thorough clinical examination of all children and adults. In a children's institution, you should check the attendance table for the last month, do not take new children to the group where the person was diagnosed, and do not transfer children from this group to another. It is also necessary to ensure that maintenance personnel are assigned to groups. The spread of hepatitis A, the appearance of the disease in other groups contributes to the violation of the sanitary-hygienic regime, isolation between groups, transfer of children or personnel from quarantine to other groups. Admission of new children to these facilities is allowed with the permission of the epidemiologist, provided that he is given immunoglobulin beforehand, or even better, after administering at least one dose of hepatitis A vaccine (havriks, avaxime, GEP-A-in-VAK, etc.)

After isolation of the first patient, all contactees should be under close clinical supervision during the full period of quarantine - 35 days from the date of isolation of the last patient.

Everyone who has been in contact every day is examined skin, sclera, mucous membranes, necessarily the first examination shows the size of the liver and spleen, fixing the color of urine and feces.

In the hepatitis A focus for the identification of atypical, erased and subclinical forms, it is recommended to conduct laboratory tests: determine the activity of ALT and a specific marker - anti-HAV IgM class in the blood serum (blood for the study is taken from the finger). These studies can be repeated every 10 to 15 days before the end of the outbreak. With the help of these studies, it is possible to identify virtually all infected and quickly localize the focus of infection.

Suppression of transmission paths

Strict control of public catering, drinking water quality, observance of public and personal hygiene is crucial for stopping transmission routes. Given the prevalence of morbidity among organized children, special attention should be given to the sanitary condition and the anti-epidemic regime in pre-school institutions, schools, boarding schools and other children's institutions.

When a patient with hepatitis A is identified in the focus of infection, current and final disinfection is carried out in strict accordance with the orders of the Ministry of Health.

Increased immunity to HAV infection

Among the measures aimed at increasing the immunity of the population to hepatitis A, the introduction of normal immunoglobulin is of some importance. Numerous studies have shown that the timely use of immunoglobulin in the hepatitis A site, along with other anti-epidemic measures, contributes to the management of outbreaks in families and institutions. The incidence of clinically pronounced forms among immunized is reduced, in comparison with non-immunized, several times.

The prophylactic effect in immunoprophylaxis is ensured by the presence of specific antibodies (anti-NAV) of IgG class in preparations of commercial y-globulin. But since donor blood (placental and abortion) is used to make immunoglobulin preparations from women who have not had viral hepatitis, the content of antibodies to the hepatitis A virus in commercial y-globulins is often low. This is the reason for the insufficient prophylactic efficacy of many immunoglobulin preparations. In recent years, the standardization of commercial y-globulins by the titer of antibodies to hepatitis A virus has been carried out to increase the effectiveness of immunoprophylaxis. It has been shown that the best preventive effect is achieved when using an immunoglobulin with an anti-HAV titer of 1: 10 000 and more. It is usually possible to get such a high-grade immunoglobulin from the blood of donors-convalescents of hepatitis A. Currently, several drugs of highly active immunoglobulins undergoing clinical trials have been created using the new technology.

There are two types of immunization of hepatitis A: planned, or preseason, and according to epidemic indications.

Planned (preseason) prophylaxis of hepatitis A immunoglobulin in our country was conducted from 1967 to 1981. We used y-globulin (placental, from abortion blood), not titrated to anti-HAV. The drug is administered annually in a dose of 0.5-1 ml to preschool children and schoolchildren in the period preceding the seasonal rise in morbidity (August-early September).

The results of mass immunoprophylaxis showed that the overall incidence of hepatitis A in the country as a whole did not decrease, although there was a slight decrease in the number of typical icteric forms, but the number of atypical (erased and jaundiced) forms increased. At present, mandatory planned pre-seasonal immunization is abolished in our country, but as an interim measure, immunoprophylaxis is maintained according to epidemiological indications. Immunoglobulin is indicated for children from 1 year to 14 years old, as well as for pregnant women who had contact with hepatitis A in the family or children's institution for 7-10 days, counting from the first case of the disease. Children aged 1 to 10 years are administered 1 ml of 10% commercial immunoglobulin, over 10 years old and adults - 1.5 ml.

In pre-school children's institutions, with complete isolation of individual groups, immunoglobulin is administered not to the hepatitis A infected children of the group (in school-class), where the disease occurred. With incomplete isolation of groups, the question of administering immunoglobulin to children of the entire institution should be addressed individually.

Noting the anti-epidemic effect of immunoprophylaxis, we still have to admit that its possibilities are limited. Even if all the necessary conditions are met (immunization of people with full immunity, high content in anti-HAV preparations), the efficacy index does not exceed 3. In addition, it must be taken into account that the duration of protective immunity does not exceed 5-6 months, so if repeated cases occur the expiration of this period, it is necessary to resort to re-introduction of immunoglobulin, which can lead to increased sensitization, so a radical solution to the problem of preventing hepatitis A is possible only with the help of vaccines.

Hepatitis A vaccine prophylaxis

The first prototype vaccine against hepatitis A was created in 1978. Formalinized liver homogenate from HAV-infected was obtained. Currently, several variants of the inactivated vaccine against hepatitis A have been proposed. In our country, the domestic hepatitis A vaccine has been tested and cultured, inactivated, purified, liquid, GEP-A-in-VAC (Vector Vostok, Novosibirsk). This vaccine is a mixture of inactivated purified hepatitis A virions adsorbed on aluminum hydroxide. A strain of the virus LBA-86 [variant of the strain RLU-15 (American) grown on a grafted culture of 46-47 cells (kidneys of green monkeys) was used.In one dose of the vaccine (0.5 ml) contains more than 50 EIzza Units of the antigen of the hepatitis A virus, not more than 0.5 mg / ml of aluminum hydroxide and an admixture of formalin.

Of foreign commercial vaccines in Russia are registered:

• Havrix 1440 manufactured by GlaxoSmithKline (Great Britain), which is a sterile suspension containing formaldehyde inactivated hepatitis A virus (strain HM 175 of hepatitis A virus) grown in the culture of human MCH parenchymal cells adsorbed on aluminum hydroxide;
• havriks 720 of the company "GlaxoSmithKline", a children's dose;
• Avantis Pasteur (France);
• of the company "Merck Shari and Dome" (USA) - Vakta 50 ED, Vakta 250 ED;
• tweenrix - a vaccine against hepatitis A and B (GlaxoSmithKline).

A domestic vaccine was added with the addition of the immunomodulator polyoxidonium GEN A-in-VAK-POL "Hepatitis A vaccine culture purified concentrated adsorbed inactivated liquid with polyoxidonium" by Vector (Russia).

Scheme of vaccination against hepatitis A

Vaccination against hepatitis A is recommended to begin at 12 months of age. Normally, one dose is initially administered. The second dose is recommended to be administered after 6-12 months after the first dose. In the manual for the domestic vaccine against hepatitis A, a triple vaccination according to scheme 0 is recommended; 1; 6 months with subsequent revaccination every 5 years.

A vaccine against hepatitis A is injected intramuscularly into the deltoid muscle region or into the upper third of the outer surface of the thigh. In the gluteus muscle, as well as subcutaneously injecting the vaccine is not recommended because of the danger of obtaining a low level of immune response.

Vaccinal immunity

Vaccines against hepatitis A form humoral immunity to HAV. After one dose of the vaccine, the protective level of immunity is formed in 95% of the vaccinated and most of them persist for at least a year. After the second booster dose, the antibody titer dramatically increases and practically all provide reliable protection for 5 years or more. According to the main studies, the number of antibodies after administration of the vaccine is practically the same as that of patients who underwent this disease, and therefore the question of the advisability of subsequent revaccinations has not yet been finally decided.

By analogy with other inactivated vaccines, it can be assumed that post-vaccination immunity can not be prolonged and, most likely, the question of revaccinating doses will arise after 5 or 10 years. However, this issue needs further study. Theoretically, since the circulation of the hepatitis A virus is too high in Russia, it can be assumed that there is a possibility of natural booster immunization, and due to this, protective immunity will be maintained throughout life. If we proceed from such preconditions, it is quite obvious that the main task is to carry out a primary vaccination, which will be constantly fed by natural immunization. However, it is not difficult to assume that after mass vaccination against hepatitis A there will come a period when there is a sharp decline in the circulation of the hepatitis A virus. In this case, natural immunization will decrease and, most likely, there may be a decrease in the level of protection against hepatitis A, and then, possibly , the question of revaccinating doses at certain intervals will arise more sharply.

Indications for vaccination against hepatitis A

Since hepatitis A is one of the most common infections in our country, it is possible to set the goal of universal vaccination in childhood.

However, due to the high cost of the vaccine, this task is not possible.

In most developed countries, hepatitis A vaccine is recommended for people at high risk: traveling to regions with a high incidence of hepatitis A (Africa, Asia, the Middle East, Central and South America), soldiers with an occupationally high risk of hepatitis A (workers sanitary facilities, food units, medical institutions of pre-school institutions, etc.) living in regions with high circulation of epidemic clones of the causative agent of the disease, with low sanitary and hygienic m of living standards and others.

Precautions and contraindications for vaccination against hepatitis A

Inactivated vaccines against hepatitis A are contraindicated for people with hypersensitivity to vaccine components (mainly to the culture of human cells of MICS5), and if a previous dose of the vaccine has a severe allergic reaction to the type of anaphylaxis, a temporary and severe acute infection is a temporary contraindication, accompanied by a high fever.

For people with primary and secondary immunodeficiency, the hepatitis A vaccine is not contraindicated, but given the insufficient level of immunological response, the dose of the vaccine in these cases should be doubled.

Hepatitis A vaccine should be given with caution to patients who have thrombocytopenia or reduced blood clotting, because of the possibility of bleeding from the injection site. In this case, it is better to administer the vaccine subcutaneously, although the level of immunity in this case will not be so tense.

Vaccination reactions and complications

Inactivated hepatitis A vaccines are relatively non-reactogenic. Approximately 15% of people on the site of injection note a local reaction in the form of soreness, swelling, redness; 0.5% of the vaccinated patients have severe pain. Disorders of general health with headaches, malaise, a feeling of heat, chills, nausea, vomiting, loss of appetite and other symptoms are noted in no more than 3-10% of vaccinated people. They occur in the first 24 hours from the time of administration of the vaccine and go through a few hours. When the vaccine is re-introduced, the incidence of adverse reactions is much less.

The vaccine against hepatitis A can be combined with any other vaccine declared by the calendar of preventive vaccinations, provided it is injected into different parts of the body and with different syringes.