Hepatitis A vaccine belongs to the class of medications called vaccines. It is used to prevent infection by hepatitis A. The vaccine contains inactivated hepatitis A virus that is not capable of causing disease, but instead stimulates your body to produce its own protection (antibodies) against the disease. Protection against hepatitis A is usually in place within one month of injection.

Hepatitis A is a serious disease of the liver that is spread most often through infected food or water by the hepatitis A virus. This virus is much more common in areas of the world that have a lower level of sanitation and sewage systems, but can be a problem in other countries as well.

Hepatitis A vaccine will help protect you from this disease when travelling to certain areas of the world, including:

• Africa
• Asia (except Japan)
• parts of the Caribbean
• Central and South America
• eastern Europe
• the Mediterranean basin
• the Middle East
• Mexico

The vaccine is also recommended for people who live in areas that have frequent hepatitis A outbreaks or who are at increased risk for infection. These may include:

• chronic care hospital staff
• employees and children in daycare centres
• food handlers
• health care workers
• hemophiliacs and other people who receive blood products
• Indigenous peoples
• military personnel
• orphanage staff and residents
• people engaging in high-risk sexual activity
• people who eat high-risk foods (e.g., raw shellfish)
• people who handle primate animals
• people with chronic liver disease
• sewage workers
• staff of mental health care facilities
• users of illicit injectable drugs

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

A qualified health care professional will inject the hepatitis A vaccine. Havrix is not recommended for children less than one year old.

For adults (19 years of age and older), one adult dose (1.0 mL) is injected into a muscle (preferably in the outer upper arm) with a repeat ("booster") dose 6 to 12 months later. For children 1 to 18 years of age, a single pediatric dose (0.5 mL) is injected into a muscle (preferably the outer upper arm and the outer upper thigh in children up to the age of 2) with a booster dose 6 to 12 months later.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important this vaccine be given exactly as recommended by your doctor. If you miss an appointment to receive this vaccine, contact your doctor as soon as possible to reschedule your appointment.

Keep the vaccine in its original package to protect it from light. Refrigerate the vaccine until use. If frozen, it will have to be discarded.

Each 1.0 mL dose contains 1440 ELISA units of formaldehyde-inactivated hepatitis A virus (HM175 hepatitis A virus strain) adsorbed onto aluminum in the form of aluminum hydroxide. Nonmedicinal ingredients: aluminum hydroxide, amino acids for injection, disodium phosphate, monopotassium phosphate, neomycin sulphate (less than 20 ng), polysorbate 20, potassium chloride, sodium chloride, and water for injection.

Do not use hepatitis A vaccine if you:

• are allergic to any ingredient of the vaccine
• have an acute, severe illness with fever

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• drowsiness
• fatigue
• fever
• generally feeling unwell
• headache
• irritability
• loss of appetite
• muscle or joint achiness
• nausea or vomiting
• pain and redness at the injection site
• swelling or hard lump at the injection site
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Seek immediate medical attention if any of the following side effects occur:

• symptoms of a serious allergic reaction (e.g., hives, difficulty breathing, or swelling of the face or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Bleeding disorders: If you have any bleeding problems (such as hemophilia) or are taking blood thinners such as warfarin, tell your doctor before receiving this medication.

Cancer and immunosuppression: Hepatitis A vaccine may not be as effective if you have cancer, if you are receiving immunosuppressive therapy (e.g., some medications used to treat cancer or for transplant recipients), or if you are immunocompromised (i.e., your immune system does not work properly).

Immunization record: Make sure any new doctors know that you have had this vaccination so that they can put this information in your immunization record.

Infection and fever: If you have an infection or fever, your doctor may recommend that you wait until you are better before receiving the hepatitis A vaccine.

Neomycin allergy: The vaccine may contain trace amounts of neomycin and thus may cause an allergic reaction in people who are allergic to neomycin.

Vaccine protection: As with any vaccine, this vaccine may not result in total protection from hepatitis A and may not prevent hepatitis A for people who are infected with the virus at the time of vaccination.

Pregnancy: This vaccine should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if the vaccine passes into breast milk. If you are a breast-feeding mother and are plan to receive this vaccine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children below the minimum age stated above.

There may be an interaction between the hepatitis A vaccine and any of the following:

• medications that suppress the immune system:
• corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
• medications used to treat conditions such as cancer, inflammatory bowel disease, multiple sclerosis, psoriasis, rheumatoid arthritis, or medications used after a transplant

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.