Hepatitis A vaccine

Hepatitis A vaccine is a prescription medication belonging to the vaccine class.

The hepatitis A vaccine is approved for use in immunization against hepatitis A virus infection, protecting against viral disease, particularly for children and individuals who are at risk of exposure. Hepatitis A infection occurs through the fecal-oral route, most often through contaminated food and water. It is usually used in routine immunisation programmes, especially in areas where there is a high risk of developing hepatitis A infection.

The hepatitis A vaccine is administered via injection, and the antigens stimulate the immune system. There is no significant metabolism or elimination; instead, it prompts the body to produce antibodies for future protection against hepatitis A.

The common side effects of the hepatitis A vaccine include injection site pain, redness, mild fever, and fatigue.

The Hepatitis A vaccine is available in the form of injectable solutions.

Hepatitis A vaccine is available in the United States, Canada, Germany, Russia, the United Kingdom and Australia.

The hepatitis A vaccine, belonging to the vaccine class, acts as an inactivated virus. The hepatitis A vaccination produces a strong immunological response. The white blood cells, specifically lymphocytes, become activated in response to possible infections. Immune cells engulf the vaccination antigens, causing the production of inflammatory mediators. These signals activate and stimulate B and T cells to produce antibodies and target the vaccination antigen. B cells differentiate into specialized cells, such as antibody-producing B and memory cells, whereas T cells differentiate into cytotoxic and helper T cells. This integrated immune response results in long-lasting protection in the event of future hepatitis A virus exposure.

Many vaccines, including the hepatitis A vaccine, comprise adjuvants, which boost the immune system's reaction. The aluminium in the hepatitis A vaccination inhibits the absorption of injected antigens, resulting in a concentrated antigen presence at the injection site. Also, aluminium can directly activate intrinsic immune system cells, causing the release of inflammatory mediators and increasing the immunological response.

Onset: 4 week

The length of disease protection is long-lasting (years), although the onset of it is relatively slow.

The Hepatitis A vaccine is available in the form of injectable solutions.

Injectable solutions: To be administered parenterally, as applicable.

A healthcare professional administers the injectable hepatitis A vaccine. It requires a two-dose series for complete protection, with the second dose given at least six months after the first. Booster shots are also required for long-term immunity.

Hepatitis A vaccine can be used as follows:

• To protect against hepatitis A infection in people, especially children.

• To protect travellers who are visiting regions with a high prevalence of hepatitis A incidence.

• To protect high-risk populations, individuals with underlying medical conditions or at high risk should be given immunity.

• To provide post-exposure prophylaxis in outbreak situations such as during epidemics.

Hepatitis A vaccine can help support the following health benefits:

• Prevention: Hepatitis A is a highly infectious liver disease condition caused by the hepatitis A virus, and its prevention is the primary benefit of the hepatitis A vaccination. The vaccine provides essential protection and lowers the risk of severe illness and hospitalization, making it the most effective way to prevent acquiring the virus.
• Lifelong immunity: Long-lasting protection can be obtained by the hepatitis A vaccination. Most people who receive the recommended two-dose series develop immunity that may persist for many years, if not a lifetime. In most situations, this eliminates the requirement for booster shots and provides hepatitis A protection.

• Herd immunity: Public health benefits greatly from extensive hepatitis A vaccinations. The possibility for severe hepatitis A ramifications among them is reduced. It protects the person who was vaccinated and those individuals with weaker immune systems, children, the elderly, and vulnerable populations.

Hepatitis A vaccine is approved for its use in the following clinical indications:

• The Hepatitis A vaccine is administered to people who are at risk of developing the hepatitis A virus (HAV). People who work with primates infected with the hepatitis A virus or in a hepatitis A virus laboratory should be vaccinated.
• Indicated in individuals over the age of 40 who have recently been exposed to the hepatitis A virus and individuals over the age of 40 if hepatitis A immunoglobulin cannot be acquired
• It is recommended for HIV patients over the age of one year.
• Persons working in or travelling to areas with high or intermediate epidemics of HAV infection should be vaccinated at the appropriate age.
• Travellers to places with high HAV prevalence, those with specified medical conditions, men who have sex with males, and specific professional categories are all advised to get this vaccine.
• Individuals with long-term liver disease or weakened immune systems may be given the hepatitis A vaccine to avoid severe problems if exposed to the virus.
• Pregnant women at risk of hepatitis A (HAV) due to travel, drug use, occupational exposure, or chronic health issues should be vaccinated to avoid serious illness or complications.
• Food handlers are indicated with hepatitis A vaccine and may contract hepatitis A and possibly transmit the virus to others.

Parenterally: The hepatitis A vaccine is given parenterally, administered only as an intramuscular injection, which means it is injected directly into a muscle, usually the deltoid muscle that is in the upper arm for adults or the thigh muscle for young children as a single dose injection and can be only given by a healthcare professional in a hospital setting or during routine immunization programs.

The dosage and duration of treatment should be as per the clinical judgme of the treating physician.

Injectable solutions

• For adult dose: 50 units/mL (Vaqta)

1440 ELISA units/mL (Havrix)

• For pediatric dose: 25 units/0.5 mL (Vaqta)

720 ELISA units/0.5mL (Havrix)

Dosage Adjustment for Adult Patients

Hepatitis A Immunization

Indicated as an active immunization for all individuals who require protection and for those at risk of developing HAV infection

2 dose vaccination series

19 years or older: 1 mL intramuscularly (baseline dosage)

Administer baseline dose at least 2 weeks prior to expected HAV exposure (Advisory Committee on Immunization Practices – ACIP guidelines)

Havrix: Administer a booster dose between 6 to 12 months after baseline dose

Vaqta, Administer a booster dose between 6 to 18 months after the baseline dose.

Pre-exposure protection against HAV for travelers (ACIP guidelines)

1 mL intramuscularly administered at least two weeks before HAV exposure

When considering travel, those who have not previously received the hepatitis A vaccination should administer the first dose and finish the complete 2-dose series on schedule.

For individuals who are immune deficient or have chronic liver disease, are older than 40, and are otherwise healthy, consider providing immune globulin as well.

PEP for HAV (Post-Exposure Prophylaxis)

1 mL intramuscularly

When a second dose is unnecessary for PEP, complete the 2-dose series for long-term immunity.

Age more than 40 years: Consider the requirement also to provide immunoglobulin.

Immunosuppressed patients or those with chronic liver disease should get both the vaccine and immune globulin simultaneously and at different anatomic locations.

The Hepatitis A vaccine is available in the form of injectable solutions.

Hepatitis A vaccine should be used to prevent hepatitis infection in children and individuals at high risk, along with no appropriate dietary restrictions.

Hepatitis A vaccine usually has little effect on dietary or food substances when administered. For infants, regular diet, including breastfeeding or formula feeding, is safe before and after receiving the vaccine. In contrast, for adults, consuming normal foods and drinks before and after receiving the vaccine is safe.

It is commonly advised to stay well hydrated by drinking water or other fluids. Maintaining a balanced diet can help boost the body's immunological response to the vaccine and overall health during vaccination.

The dietary restriction should be individualized as per patient requirements.

Hepatitis A vaccine may be contraindicated in the following conditions-

• Hypersensitivity (previous dose of vaccine or any of its components)
• Allergic to latex rubber
• Guillain-Barré Syndrome (GBS) after an earlier dose.
• Pregnancy (often not advised unless a considerable risk of infection occurs)

The treating physician must closely monitor the patient and keep pharmacovigilance as follows.

• If the infant has a moderately critical acute sickness (with or without fever), administration of the vaccine should be postponed.
• Although the vaccine is generally safe for pregnant or breastfeeding women, it should only be administered with a high risk of hepatitis infection.
• Individuals with cancer or weakened immune systems with frequent close contact with a child receiving this vaccine may have a rare risk of hepatitis transmission.
• It is recommended not to reconstitute or dilute the vaccine before administration.
• Depending on individual risk factors and exposure, it is recommended to take booster doses for long-term protection.

Caution is advised when consuming alcohol with the hepatitis A vaccine.

There is no sufficient scientific evidence regarding the use and safety of the hepatitis A vaccine in the breastfeeding population.

Safe to use during pregnancy.

The adverse reactions related to the hepatitis A vaccine can be categorized as

• Common: Tenderness, erythema, warmth, swelling at the site of injection, irritability, anorexia, drowsiness, headache, fever more than100.4 F
• Less common: Upper respiratory infection, otitis media, rhinorrhoea, diarrhoea, cough, rash, weakness/fatigue, vomiting, fever more than 102 F, crying
• Rare: Hematoma, increased Creatine phosphokinase (CPK), photophobia and vertigo

The clinically relevant drug interactions of the Hepatitis A vaccine are briefly summarized here:

• Immunosuppressants- The immunological response to Hepatitis A vaccine may be suppressed by immunosuppressive treatments such as radiation, antimetabolites, alkylating agents, cytotoxic medicines, and corticosteroids (used in dosages larger than therapeutic doses).
• Immunoglobulins: Immunological globulins, such as intravenous immunoglobulin (IVIG), can interfere with the immunological response to the Hepatitis A vaccine when administered concurrently. The vaccination may need to be administered more often or in greater doses for optimal outcomes.

• Other Vaccines- Multiple vaccinations, including Hepatitis A vaccine, given at the same time may increase the risk of adverse reactions. To reduce such a risk, medical professionals frequently adhere to vaccination regimens considering the time and space of vaccines.

The common side of the Hepatitis A Vaccine includes the following-

• Pain, swelling, redness or tenderness at the injection site
• Low-grade fever
• Mild headache
• Fatigue
• Tiredness
• Headache
• Nausea
• Diarrhea
• Stomach discomfort

The use of Hepatitis A Vaccine should be prudent in the following group of special populations.

• Pregnancy:

Pregnancy Category: C. Safe during pregnancy, but when taken in high doses, use with caution if the benefits outweigh the risks.

Hepatitis A Vaccine is usually considered safe during pregnancy; it is mostly advised when there is a significant risk of hepatitis exposure. Unless the risk of exposure is very high, routine vaccinations are normally not recommended during pregnancy.

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• Paediatrics:

In paediatrics, the hepatitis A vaccination prevents severe liver disease, reduces transmission, and provides long-lasting protection, improving overall health and lowering the risk of infection in children and those who surround them.

Dosage Adjustment for Paediatric Patients

Hepatitis A Immunization

According to ACIP recommendations, children at least 12 months old should receive this immunization routinely.

Less than 12 months: It is generally not indicated, but if administered, it should not be counted toward the routine 2-dose series

12-month-olds to 18-year-olds (2-dose series)

Primary dose: 0.5 mL intramuscularly

Havrix: Administer booster dose 6 to12 months after baseline dose

Vaqta: Administer booster dose 6 to18 months after baseline dosage

Children who have been administered 1 dose before age 24 months should receive a second dose at 6 to18 months after the first dose

Catch up schedule

Any person ≥2 years who has not already received the hepatitis A vaccine series should be given 2 doses separated by 6 to 18 months but only if immunity against hepatitis A virus infection is effective

The minimum interval between the 2-dose series is 6 months

Pre-exposure protection against HAV for travellers (ACIP guidelines)

Less than 6 months: Administer immune globulin rather than the hepatitis A vaccinations

6 to 11 months: 0.5 mL intramuscularly, but this dose does not count toward routine 2-dose vaccination series

12 months through 18 years: 0.5 mL intramuscularly but if not previously vaccinated with hepatitis A vaccine. It is required to complete 2-dose series according to a routine schedule

Immunocompromised or chronic liver disease: 0.5 mL intramuscularly but also administer immune globulin

Postexposure prophylaxis (PEP) for HAV

12 months through 18 years: Administer 0.5 mL intravenously, but if not previously vaccinated with hepatitis A vaccine, it is required to complete 2-dose series according to a routine schedule

Immunocompromised or prolonged liver disease: Immune globulin and vaccine should be administered simultaneously at different anatomic sites

International travel

Those travelling to or working in nations where hepatitis A infection rates are high or moderate.

Infants aged 6 to 11 months: 1 dose prior to departure; 2 doses of revaccination between 12 and 23 months of age, separated by at least 6 months

Unvaccinated >12 months: Administer 1 dose as soon as travel is considered and dose 2 after six months.

• Geriatrics:

There is no sufficient scientific evidence traceable regarding the use and safety of the Hepatitis A vaccine for geriatric populations.

• Lactating mothers:

There is no sufficient scientific evidence traceable regarding the use and safety of the Hepatitis A vaccine for lactating mother populations.

Dosage Adjustment in Kidney Impairment

There are no specific dosage adjustments provided.

Dosage Adjustment in Hepatic Impairment

There are no specific dosage adjustments provided.

Overdosage of Hepatitis A vaccine rarely occurs because healthcare professionals administer it according to specific or precise dosing guidelines. Still, if it were to happen then it may include symptoms such as severe allergic reactions, high fever, pain at the injection site, weakness, nausea, vomiting, diarrhoea and jaundice.

There is no specific antidote or treatment for excessive intake of Hepatitis A vaccine. Medical attention should be sought immediately when an overdose is suspected, followed by close monitoring for any adverse effects or allergic reactions. Supportive therapy should also be given, addressing any symptoms that persist or worsen. Physical treatment might be added if necessary.

Pharmacodynamics of Hepatitis A vaccine:

The Hepatitis A vaccine is an essential method for preventing Hepatitis A infection. When administered, it stimulates the immune system to produce anti-Hepatitis A antibodies, which play a crucial role in protecting the body from this viral disease. These antibodies are mainly designed to target the Hepatitis A virus, rendering it inactive and preventing it from getting sick.

Furthermore, the vaccine activates several immune cells, including T and B cells, which work together to give adequate and long-lasting protection. T cells detect and destroy infected cells, whereas B cells make antibodies to provide long-term protection. Thus, the immune response ensures that people who receive the Hepatitis A vaccine are well-protected from infection while maintaining good health in case of potential Hepatitis A virus exposure.

Pharmacokinetics of Hepatitis A vaccine:

• Absorption: After administration, the vaccine's components, which include inactivated HAV particles or a subunit of the virus, are introduced into the bloodstream, and they initiate an immune response.
• Distribution: The vaccine antigens travel throughout the body via the bloodstream. They are recognized by immune cells, mainly B cells, which play a critical role in the immunological response.
• Metabolism: Vaccines do not undergo metabolism in the liver or other organs. Instead, the immune system processes the vaccine antigens. Antigens are recognized as foreign by B cells, and antibodies are produced against them.
• Elimination: The hepatitis A vaccination is not eliminated. Instead, the immune system initiates an immunological reaction to the vaccination antigens, producing hepatitis A-specific antibodies. These antibodies help to protect the body from future hepatitis A infections by attaching to and neutralizing the virus.

• Iino, S et al. Nihon Shokakibyo Gakkai zasshi. The Japanese Journal of gastro-enterology vol. 87,7 (1990): 1532-6.
• Verma, Ramesh, and Pardeep Khanna. "Hepatitis A vaccine should receive priority in National Immunization Schedule in India." Human vaccines &immunotherapeutics vol. 8,8 (2012): 1132-4. doi:10.4161/hv.20475
• Tilzey, Anthea J., et al. "Clinical Trial With Inactivated Hepatitis A Vaccine And Recommendations For Its Use." BMJ: British Medical Journal, vol. 304, no. 6837, 1992, pp. 1272–76. JSTOR, http://www.jstor.org/stable/29715592. Accessed 5 Sept. 2023.

• Inform the caregivers of the schedule for administering the hepatitis A vaccine doses, including the specific ages they should be given.
• Inform the vaccination recipient, their parents, or their guardians whether they had any side effects from a prior dosage of the hepatitis A vaccine.
• Assure caregivers that rotavirus immunizations are generally safe, with only minor, short side effects. Encouraging them to immediately report any unexpected or severe responses to the healthcare physician and, whenever applicable, to use reporting systems like the Vaccine Adverse Event Reporting System (VAERS)
• Inform caregivers of the recommended immunization schedule, which usually consists of two or three doses, depending on the vaccine brand used. Also, mention the ages at which the doses should be administered and give the Vaccine Information Statements, which must be disclosed before immunization by the National Childhood Vaccine Injury Act of 1986 about the Centers for Disease Control and Prevention (CDC) website (www.cdc.gov/vaccines), these resources are freely accessible.

• http://www.cdc.gov/vaccines/default.htm
• https://www.ncbi.nlm.nih.gov/books/NBK554604/
• https://www.cdc.gov/vaccines/hcp/vis/vis-statements/hep-a.html
• Coffman RL, Sher A, Seder RA. Vaccine adjuvants: putting innate immunity to work. Immunity. 2010 Oct 29;33(4):492-503.