Hepatitis A vaccine

Hepatitis A is an acute infectious disease caused by an RNA-containing virus that spreads by the fecal-oral route. In regions with a low sanitary standard of living, the incidence peak falls on early childhood and preschool age; Hepatitis A in children usually proceeds in mild form, becoming immune for life.

In urban areas, the incidence is shifting to adolescents and adults, who have more severe hepatitis A, often with relapses for many months. In Russia, with an infection reservoir in rural areas and a susceptible stratum in cities, in close contact between them, outbreaks (often food or water) occur annually.

In Russia, the incidence of hepatitis A in the early 21st century increased and was in 2001 (per 100,000) 79.5 (in children -183.6) In 2007, the incidence decreased to 10.23 (in children under 14 years of age - 24.12), which is associated, including, with the vaccination in the outbreaks.

Hepatitis A does not give chronic forms, but with a layering on chronic hepatitis B or chronic hepatitis C can occur in fulminant form.

Objectives of vaccination against hepatitis A

Mass vaccination is conducted in Israel, Spain and Italy; Since 2006, double vaccination has been included in the US National Calendar for all children aged 12-24 months. The use of the vaccine is aimed at long-term protection of children, as well as protection of persons who have not had hepatitis A in childhood. Vaccination for epidemics can quickly stop the outbreak of hepatitis A, which has been demonstrated in several regions of Russia.

Vaccinations indicated in patients with chronic liver disease (including chmsle media HBsAg and hepatitis C virus ), employees catering. Military contingents engaged in the field are also being vaccinated.

Vaccination against hepatitis A: characteristics of vaccines

In Russia, several vaccines of the same type have been registered: all of them are administered intramuscularly (preferably) or subcutaneously, the full course consists of 2 doses with an interval of 6-18 months, patients with hemodialysis, with immunity defects, an additional dose is recommended after 1 month. After the first. In addition to monovaccine, 2 combined vaccines against hepatitis A and B (GEP-A + B-in-VAK and Tweenrix) were registered.

Hepatitis A vaccines registered in Russia

Vaccines	Content	Doses
GEP-A-INVAK, Russia	Virions strain LBA-86, grown on cell culture 4647, adsorbent-aluminum hydroxide. In 1 ml> 50 ELISA unit. (25 ng) Without antibiotics and preservatives	Children 3-17 years old -0.5 ml, adults - 1.0 ml
GEP-A-INVAC-Paul, Russia	The same vaccine with polyoxidonium
Avaxim sanofi nacmep, France	Inactivated GBM strain virus grown on MRC 5 cells . Contains up to 0.3 mg of aluminum hydroxide, 2.5 μl of 2-phenoxyethanol, 12.5 μg of formaldehyde	Syringe-dose 0.5 ml vaccine - for children from 2 years of age and adults
Vacta® 25 Unit. And 50 Units. Merck, Sharpe and Dome, USA	Formalin-inactivated strain of virus RC 326F, grown on a monolayer of MRC 5 cells . Activity: 50 U / ml, contains aluminum hydroxide (0.45 mg / ml), traces of formaldehyde. Without preservative	Children 2-17 years old 25 AE - 0.5 ml, adults 50 AE - 1.0 ml
Havriks 720 and 1440 Glaxo-SmithCleine, Belgium	A virus suspension obtained by lysing infected MRC 5 cells inactivated with formalin and adsorbed on an aluminum hydroxide gel.	Syringe dose 0.5 ml for children 1-16 years and 1.0 ml for persons> 16 years
Epaxal Berna Biotech, Switzerland. Submitted for registration	Technology using virosome complexes (liposomal membrane of lecithin and cephalin).

Immunogenicity and epidemiological efficacy

The protective effect of vaccination is evident from the end of the first week, the duration of protection after the introduction of the second dose, according to modeling> 25 years. GEP-A-in-BAC after complete course gives seroconversion at least 95% of adults and 90% of children.

Avaxim stimulated the seroprotective level (> 30 IU / L) after 1 week. After a single injection in 90% of the vaccinated, after 2 weeks. - in 98.3% of the vaccinated, after 4 weeks. 100% (elimination of the outbreak after 7 days after 1 dose without immunoglobulin).

In a study of 2,000 people, Vacta showed 100% efficacy 10 days after the 1st dose, the risk of hepatitis A in the vaccine was 0.7 per 1 million doses.

Havrix induces antibodies after 15 days in 88% of adults, after 1 month - in 99% and after the second dose - in 100%; The vaccine was widely used in outbreaks of hepatitis A in Russia with good effect.

Preservation of protective antibody titers (at zero morbidity) 3-5 years after the single administration of the vaccine Avaxim and a number of others allows postponing the introduction of the second dose: for Havriks this period is indicated as 5 years. When mass immunization with 1 dose of Vact 66% of the child population in California, the total incidence of hepatitis A declined by 94%. (11 cases with 16 million vaccinated).

Maternal antibodies to hepatitis A virus reduce antibody titres after vaccination (although they far exceed the protective level) by 12 months this effect disappears; At this age, the simultaneous administration of other vaccines does not reduce immunogenicity. Simultaneous administration of immunoglobulin and a vaccine may accelerate the onset of protection against the disease, but the antibody titre is sometimes reduced.

Serological testing of children before vaccination is not recommended, but given the high cost of the vaccine in groups of people with a history of hepatitis A in the past, testing can be economically viable.

Contraindications and side effects after inoculation from hepatitis A

Vaccines are not administered to persons with hypersensitivity to vaccine components (aluminum hydroxide, phenoxyethanol, etc.). There are no data on vaccinations of pregnant women, so vaccination should be carried out only when absolutely necessary.

Vaccination is rarely accompanied by malaise, headache, subfebrile condition, small edema at the injection site for 1-2 days, even more rarely - a transient increase in the activity of transaminases, a protein in the urine.

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Postexpositional prophylaxis of hepatitis A

The most effective method is vaccination against hepatitis A in the outbreaks; it can be combined with an immunoglobulin to persons who have had close contact. The same tactics are possible if rapid prevention is required (travel to an endemic area).

Passive immunoglobulin prophylaxis is done single-handedly to children from family or close contact in a children's institution in terms of up to the 2nd week: at the age of 1-6 years at a dose of 0.75 ml, 7-10 years - 1.5 ml, over 10 years, adolescents and adults - 3.0 ml. In the United States, the dose is calculated at the rate of 0.02 ml / kg. Repeated administration of immunoglobulin for the prevention of hepatitis A is carried out no earlier than 2 months.