What to Know About the Hepatitis A Vaccine

The hepatitis A vaccine is used to prevent hepatitis A, a viral infection of the liver that affects an estimated 1.4 million people around the world each year and occurs in scattered outbreaks throughout the United States.

There are three different hepatitis A vaccines approved by the Food and Drug Administration (FDA):

• Havrix, approved for use in 1995
• Vaqta, approved for use in 1996
• Twinrix (hepatitis A and B vaccine), approved for use in 2001

Both Havrix and Vaqta are delivered by injection in two doses and are equally effective in preventing hepatitis A infection. They can be used interchangeably. Twinrix requires three to four doses.

Hepatitis A vaccines are inactivated vaccines, meaning that they contain dead hepatitis A viruses that cannot cause disease but can still provoke an immune response.

Hepatitis A vaccines, like all vaccines, stimulate the production of immune cells, called antibodies, that "recognize" the virus and attack if exposure occurs. By doing so, the vaccine can help avert an infection.

Uses

Havrix and Vaqta are used for immunization against hepatitis A in people 12 months of age and over. Immunization describes the action of making a person immune to infection, typically by way of a vaccine but also due to natural exposure. The advantage of a vaccine is that you don't experience the symptoms and potential harms of a natural infection.

Hepatitis A infection typically occurs via the fecal-oral route, most often through contaminated food and water. The disease is prevalent in countries with poor sanitation but also occurs in the United States, largely due to person-to-person contact (e.g., sexual contact, shared drug use, or caring for someone with hepatitis A).

The annual incidence of hepatitis A in the United States has been on the rise since 2016 with an estimated 24,900 cases occurring in 2018 alone.

Indications

Vaccination for hepatitis A involves an initial injection followed by a booster shot at least 6 months later, depending on the vaccine. Together, the two doses appear to be effective for at least 20 years and possibly a lifetime.

According to the Centers for Disease Control and Prevention (CDC), hepatitis A vaccination is also recommended for people who are either at high risk of exposure or are likely to experience severe symptoms or liver injury if an exposure were to occur. These include:

• People with chronic liver diseases, including hepatitis B and hepatitis C
• People living with HIV
• Men who have sex with men
• People experiencing homelessness
• Illicit drug users (both injecting and non-injecting)
• Pregnant people who are at an increased risk of infection or severe outcomes if infected
• People who travel to a country where hepatitis A is endemic
• People in close contact with an international adoptee
• Those with an occupational risk of exposure

In addition, the CDC says that the vaccine may be given to anyone who requests it.

Before Use

Neither Havrix nor Vaqta should be given to people who have had a severe allergic reaction to a previous dose of the vaccine or any of the components of the vaccine, including neomycin.

The prefilled syringes used to deliver the vaccine are made with natural latex and should be avoided by anyone with a severe latex allergy. For these individuals, single-use vials with a separate needle and syringe should be used.

Other Options

In addition to Havrix and Vaqta, there is a combination vaccine called Twinrix that protects against hepatitis A and hepatitis B. It requires three or four doses and is only approved for people 18 years and older.

In addition to vaccines, a treatment called immunoglobulin (IG) therapy can be used to help prevent hepatitis A infection (before or after exposure). There is one IG drug approved by the FDA called GamaSTAN S/D.

GamaSTAN is delivered by injection and made from antibodies that have been harvested from donated blood. The indications vary by the aims of therapy:

• Pre-exposure prophylaxis: GamaSTAN is indicated for people at high risk of getting or experiencing severe symptoms of hepatitis A. It can be used for primary vaccination along with the hepatitis A vaccine. For travelers to endemic areas, a single dose is recommended at least two weeks before travel. The dosage depends on the duration of the stay.
• Post-exposure IG prophylaxis: GamaSTAN is given as soon as possible after exposure at a dose of 0.1 milliliters per kilogram of body weight (mL/kg).

Dosage

Hepatitis A vaccines are available either in a single-use vial or single-use prefilled syringe, both in 0.5-mL or 1.0-mL doses. The vaccine are given by intramuscular injection (into a large muscle) by a healthcare professional.

The vaccination series varies by age and vaccine type.

Havrix and Vaqta can be used interchangeably.

Side Effects

As with all vaccines, there is a potential for side effects but most are mild and tend to resolve within a day or two. On rare occasions, severe side effects may occur.

Common

According to the pre-market clinical studies, the incidence of side effects varies slightly by vaccine type.

Loss of appetite, drowsiness, and irritability (particularly in babies) are also common.

Severe

Arguably, the greatest concern about hepatitis A vaccination is a severe, whole-body allergy known as anaphylaxis. Even so, occurrences are rare, with studies reporting few if any incidences after over 25 years of use. If anaphylaxis were to occur, it may be associated with the vaccine, vaccine components, or latex used in prefilled syringes.

Even so, such reactions are rare. The same concerns have not been noted with Vaqta.

Warnings and Interactions

Some people have experienced fainting (syncope) soon after vaccination due to a drop in blood pressure. This is a non-emergency situation with no long-term consequence. However, as injury may occur from falls, anyone given Havrix or Vaqta should be monitored for 15 minutes following the shot.

Animal studies have suggested a potential for fetal harm when using Havrix and Vaqta but that the benefits may outweigh the potential risks. The vaccines should only be used during pregnancy if immunization is clearly needed.

The effectiveness of hepatitis A vaccines may be undermined in people on immunosuppressive drugs or therapies. Immunosuppressants temper the immune response, reducing the body's ability to generate protective antibodies.

Let your doctor know if you are on any of the following:

• Chemotherapy
• High-dose corticosteroids, including prednisone
• Radiation therapy
• Disease-modifying antirheumatic drugs (DMARDs), including methotrexate

In such cases, vaccination may be recommended either before the start of therapy or after the completion of therapy.