Hepatitis A prevention

Prevention of hepatitis A is the same as for other intestinal infections. It is based on three links in the epidemic chain (source of infection, routes of transmission, and susceptible organism).

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Identifying the source of infection

The system of measures aimed at neutralizing the source of infection primarily involves early diagnostics of all cases of disease and timely isolation of patients. It should be noted, however, that in 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, as patients with atypical anicteric, latent and subclinical forms of hepatitis A, the diagnosis of which is very difficult or even impossible without the use of modern laboratory research methods. It is equally important that the maximum contagiousness in hepatitis A occurs at the end 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 current level of diagnostics of hepatitis A does not allow to effectively influence the first link of the epidemic process. Nevertheless, when the first case of the disease appears, it is necessary to identify the source of infection, conduct a thorough clinical examination of all children and adults. In the children's institution, it is necessary to check the attendance record for the last month, not to accept new children into the group where the patient was identified, and not to transfer children from this group to another. It is also necessary to ensure that the service personnel are assigned to the groups. The spread of hepatitis A, the appearance of the disease in other groups is facilitated by violation of the sanitary and hygienic regime, isolation between groups, the transfer of children or personnel from the quarantine to other groups. Admission of new children to these institutions is allowed with the permission of an epidemiologist, provided that they have previously been given immunoglobulin, and even better - after at least one dose of the hepatitis A vaccine (havrix, avaxim, GEP-A-in-VAC, etc.),

After the isolation of the first patient, all contacts must be under close clinical observation for the full quarantine period - 35 days from the day of isolation of the last patient.

All those who have been in contact undergo daily examination of the skin, sclera, and mucous membranes; the size of the liver and spleen is noted during the first examination, and the color of the urine and feces is recorded.

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

Interruption of transmission routes

Strict control of public catering, drinking water quality, and public and personal hygiene are crucial to prevent the transmission of infection. Given the predominant incidence of the disease among organized children, special attention should be paid to the sanitary conditions and anti-epidemic regime in preschool institutions, schools, boarding schools, and other children's institutions.

When a patient with hepatitis A is identified in the center of infection, ongoing 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 population's immunity to hepatitis A, the introduction of normal immunoglobulin has a certain significance. Numerous studies have shown that the timely use of immunoglobulin in the focus of hepatitis A, along with other anti-epidemic measures, helps to stop outbreaks in families and institutions. The incidence of clinically expressed forms among immunized people decreases, compared to non-immunized people, several times.

The prophylactic effect in immunoprophylaxis is ensured by the presence of specific antibodies (anti-HAV) of the IgG class in commercial y-globulin preparations. But since donor blood (placental and aborted) from women who have not had viral hepatitis is used to manufacture immunoglobulin preparations, the content of antibodies to the hepatitis A virus in commercial y-globulins is often low. This can explain the insufficient prophylactic effectiveness of many series of immunoglobulin preparations. In recent years, in order to improve the effectiveness of immunoprophylaxis, commercial y-globulins have been standardized by the titer of antibodies to the hepatitis A virus. It has been shown that the best prophylactic effect is achieved when using immunoglobulin with an anti-HAV titer of 1:10,000 and higher. Such high-titer immunoglobulin can usually be obtained from the blood of donors - hepatitis A convalescents. Currently, several preparations of highly active immunoglobulins have been created using new technology and are undergoing clinical trials.

There are two types of immunoprophylaxis of hepatitis A: planned, or pre-seasonal, and according to epidemic indications.

Planned (pre-season) prophylaxis of hepatitis A with immunoglobulin in our country was carried out from 1967 to 1981. Gy-globulin (placental, from aborted blood) was used, not titrated for anti-HAV. The drug is administered annually in a dose of 0.5-1 ml to children in preschool institutions and schoolchildren in the periods preceding the seasonal increase in the incidence of the disease (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 some decrease in the number of typical icteric forms, but the number of atypical (erased and anicteric) forms increased. At present, mandatory planned pre-season immunoprophylaxis in our country has been canceled, but immunoprophylaxis according to epidemiological indications has been retained as a temporary measure. Immunoglobulin is indicated for children from 1 year to 14 years old, as well as for pregnant women who have had contact with people with hepatitis A in the family or a child care facility for 7-10 days, counting from the first case of the disease. Children from 1 year to 10 years old are given 1 ml of 10% commercial immunoglobulin, over 10 years old and adults - 1.5 ml.

In preschool institutions, with complete isolation of individual groups, immunoglobulin is administered to children of the group (in school - class) where the disease occurred who have not had hepatitis A. In case of incomplete isolation of groups, the question of administering immunoglobulin to children of the entire institution should be decided individually.

Noting the anti-epidemic effect of immunoprophylaxis, it is necessary to admit that its capabilities are limited. Even if all necessary conditions are met (universal immunization of contact people, high content of anti-HAV in preparations), the efficiency index does not exceed 3. In addition, it is necessary to take into account that the duration of protective immunity does not exceed 5-6 months, therefore, if repeated cases of the disease occur after this period, it is necessary to resort to repeated administration of immunoglobulin, which can lead to increased sensitization, therefore, a radical solution to the problem of hepatitis A prevention is possible only with the help of vaccines.

Vaccination against hepatitis A

The first prototype of the hepatitis A vaccine was created in 1978. Formalized liver homogenate from HAV-infected individuals was obtained. Currently, several variants of inactivated hepatitis A vaccine have been proposed. In our country, a domestic hepatitis A vaccine, cultured, inactivated, purified, liquid GEP-A-in-VAC (MP Vector, Novosibirsk), has been tested and approved for use. This vaccine is a mixture of inactivated purified hepatitis A virions adsorbed on aluminum hydroxide. The LBA-86 virus strain [a variant of the RLU-15 strain (American) grown on a grafted cell culture of 46-47 (green monkey kidneys)] was used. One dose of the vaccine (0.5 ml) contains more than 50 ЕІіza Units of hepatitis A virus antigen, no more than 0.5 mg/ml of aluminum hydroxide and an admixture of formalin.

Of the foreign commercial vaccines registered in Russia:

• Havrix 1440 manufactured by GlaxoSmithKline (UK), which is a sterile suspension containing formaldehyde-inactivated hepatitis A virus (hepatitis A virus strain HM 175), grown in a culture of human parenchymatous cells MKS, adsorbed on aluminum hydroxide;
• Havrix 720 by GlaxoSmithKline, pediatric dose;
• Avaxim from Aventis Pasteur (France);
• Vakta from the company "Merck Chari & Dohme" (USA) - Vakta 50 U, Vakta 250 U;
• Twinrix - a vaccine against hepatitis A and B (GlaxoSmithKline).

A domestic vaccine with the addition of the immunomodulator polyoxidonium GEN A-in-VAC-POL “Vaccine against hepatitis A, cultured, purified, concentrated, adsorbed, inactivated liquid with polyoxidonium” was created by the company Vector (Russia).

Hepatitis A Vaccination Schedule

It is recommended to start vaccination against hepatitis A from the age of 12 months. One dose is usually administered initially. The supporting second dose is recommended to be administered 6-12 months after the first dose. The instructions for the domestic hepatitis A vaccine recommend three vaccinations according to the schedule 0; 1; 6 months with subsequent revaccination every 5 years.

The hepatitis A vaccine is administered intramuscularly into the deltoid muscle or into the upper third of the outer thigh. It is not recommended to administer the vaccine into the gluteal muscle or subcutaneously due to the risk of obtaining a low level of immune response.

Vaccine immunity

Vaccines against hepatitis A form humoral immunity to HAV. After one dose of the vaccine, a protective level of immunity is formed in 95% of those vaccinated and in most of them it lasts for at least a year. After the second booster dose, the antibody titer increases sharply and provides reliable protection for almost everyone for 5 years or more. According to control studies, the amount of antibodies after the use of the vaccine is practically no different from that in patients who have had this disease, and therefore the question of the advisability of subsequent revaccinations has not yet been finally resolved.

By analogy with other inactivated vaccines, it can be assumed that post-vaccination immunity cannot be long-lasting and, most likely, the question of revaccination doses will arise in 5 or 10 years. However, this issue requires additional 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. Based on such premises, it is quite obvious that the main task is to carry out primary vaccination, which will be constantly fed by natural immunization. At the same time, it is easy to assume that after mass vaccination against hepatitis A, a period will come when there will be a sharp decrease in the circulation of the hepatitis A virus. In this case, natural immunization will decrease and, most likely, the level of protection against hepatitis A may decrease, and then, perhaps, the question of revaccination doses at certain intervals will become more acute.

Indications for vaccination against hepatitis A

Since hepatitis A is an extremely common infection in our country, the goal of universal vaccination in childhood can be set.

However, due to the high cost of the vaccine, it is not possible to solve this problem.

In most developed countries, the hepatitis A vaccine is recommended for people from high-risk groups: those traveling to regions with a high incidence of hepatitis A (Africa, Asia, the Middle East, Central and South America), military personnel, those with a high professional risk of contracting hepatitis A (health workers, food service workers, medical institutions, organized preschool institutions, etc.), those living in regions with a high circulation of epidemic clones of the pathogen, with a low sanitary and hygienic standard of living, etc.

Precautions and contraindications for hepatitis A vaccination

Inactivated hepatitis A vaccines are contraindicated in people with hypersensitivity to vaccine components (primarily to the human MRC5 cell culture), as well as in cases where a severe allergic reaction such as anaphylaxis was observed to a previous dose of the vaccine. A temporary contraindication is moderate to severe acute infection accompanied by high fever.

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

Hepatitis A vaccine should be administered with caution to patients with thrombocytopenia or decreased blood clotting, due to 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 be less intense.

Vaccination reactions and complications

Inactivated hepatitis A vaccines are relatively low reactogenic. About 15% of people experience a local reaction at the injection site in the form of pain, swelling, redness; 0.5% of those vaccinated experience severe pain. General malaise with headaches, malaise, fever, chills, nausea, vomiting, loss of appetite and other symptoms are observed in no more than 3-10% of those vaccinated. They occur in the first 24 hours after the vaccine is administered and disappear within a few hours. With repeated administration of the vaccine, the frequency of adverse reactions is significantly lower.

The hepatitis A vaccine can be combined with any other vaccine declared in the calendar of preventive vaccinations, provided that they are administered in different parts of the body and with different syringes.