Hepatitis A vaccination

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

In cities, the incidence shifts to teenagers and adults, for whom hepatitis A is more severe, often with relapses for many months. In Russia, with a reservoir of infection in rural areas and a susceptible layer in cities, with close contact between them, outbreaks (often food or waterborne) occur annually.

In Russia, the incidence of hepatitis A increased at the beginning of the 21st century and in 2001 was (per 100,000) 79.5 (in children - 183.6). In 2007, the incidence decreased to 10.23 (in children under 14 - 24.12), which is associated, among other things, with vaccination in foci.

Hepatitis A does not produce chronic forms, but when superimposed on chronic hepatitis B or chronic hepatitis C, it can occur in a fulminant form.

Goals of Hepatitis A Vaccination

Mass vaccination is carried out in Israel, Spain and Italy; since 2006, two-dose vaccination has been included in the US National Calendar for all children aged 12-24 months. The purpose of the vaccine is to provide long-term protection for children, as well as protection for individuals who did not have hepatitis A in childhood. Vaccination according to epidemiological indications allows for a rapid end to a hepatitis A outbreak, which has been demonstrated in a number of regions of Russia.

Vaccinations are indicated for patients with chronic liver diseases (including carriers of HBsAg and hepatitis C virus ), public catering workers. Military personnel engaged in field conditions are also vaccinated.

Hepatitis A Vaccination: Vaccine Characteristics

Several similar vaccines are registered in Russia: all of them are administered intramuscularly (preferably) or subcutaneously, the full course consists of 2 doses with an interval of 6-18 months, for patients on hemodialysis, with immune deficiencies, an additional dose is recommended 1 month after the first. In addition to monovalent vaccines, 2 combined vaccines against hepatitis A and B (HEP-A+B-in-VAC and Twinrix) are 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 units (25 ng) Without antibiotics and preservatives	Children 3-17 years old - 0.5 ml, adults - 1.0 ml
GEP-A-inVAK-Pol, 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 aluminum hydroxide, 2.5 µl 2-phenoxyethanol, 12.5 µg formaldehyde	Syringe dose 0.5 ml of vaccine - for children from 2 years old and adults
Vaqta® 25 Units and 50 units. Merck, Sharp and Dome, USA	Formaldehyde-inactivated RC 326F virus strain grown on a monolayer of MRC 5 cells. Activity: 50 U/ml, contains aluminum hydroxide (0.45 mg/ml), traces of formaldehyde. No preservative	Children 2-17 years old 25 AE - 0.5 ml, adults 50 AE - 1.0 ml
Havrix 720 and 1440 Glaxo-SmithKlein, Belgium	A virus suspension obtained by lysis of infected MRC 5 cells, inactivated with formalin and adsorbed on 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 virosomal complexes (liposomal membrane made 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 administration of the 2nd dose, according to modeling data, is >25 years. HEP-A-in-VAC after a full course gives seroconversion in at least 95% of adults and 90% of children.

Avaxim stimulated the seroprotective level (>30 IU/l) 1 week after a single administration in 90% of vaccinated persons, 2 weeks later in 98.3% of vaccinated persons, and 4 weeks later in 100% (outbreak elimination 7 days after 1 dose without immunoglobulin).

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

Havrix induces antibodies in 88% of adults after 15 days, in 99% after 1 month, and in 100% after the 2nd dose; the vaccine has been widely used in hepatitis A outbreaks in Russia with good effect.

Maintaining protective antibody titers (with zero incidence) 3-5 years after a single administration of Avaxim and a number of other vaccines allows postponing the administration of the 2nd dose: for Havrix, this period is indicated as 5 years. With mass immunization with 1 dose of Vacta of 66% of the child population in California, the overall incidence of hepatitis A decreased by 94%. (11 cases out of 16 million vaccinated).

Maternal antibodies to hepatitis A virus reduce antibody titers after vaccination (although they are still well above the protective level); by 12 months, this effect disappears; at this age, simultaneous administration of other vaccines does not reduce immunogenicity. Simultaneous administration of immunoglobulin and vaccine may accelerate the onset of protection against the disease, but antibody titers sometimes decrease.

Serologic testing of children prior to vaccination is not recommended, but given the high cost of the vaccine in groups of individuals with a history of hepatitis A, such testing may be cost-effective.

Contraindications and side effects after hepatitis A vaccination

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

Vaccination is rarely accompanied by malaise, headache, subfebrile temperature, slight swelling at the injection site for 1-2 days, and even less often by a transient increase in transaminase activity and protein in the urine.

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Post-exposure prophylaxis of hepatitis A

The most effective is the hepatitis A vaccine in foci; it can be combined with immunoglobulin for people who have had close contact. The same tactics are possible if rapid prevention is needed (travel to an endemic area).

Passive prophylaxis with immunoglobulin is administered once to children from family or close contact in a child care facility within 2 weeks: 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 USA, the dose is calculated at 0.02 ml/kg. Repeated administration of immunoglobulin for the purpose of preventing hepatitis A is performed no earlier than 2 months later.