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How It Works

Twinrix is a vaccine that provides active immunity against both the hepatitis A and hepatitis B viruses. It is given in a series of 3 injections on the same schedule as the hepatitis B vaccine: an initial dose followed by doses at 1 month and 6 months.

Why It Is Used

The vaccine can prevent infection with one series of injections rather than two series. The U.S. Food and Drug Administration (FDA) has approved its use only for people age 18 or older who are at risk of infection with the hepatitis A virus (HAV) and the hepatitis B virus (HBV). These include people who:

• Will travel to areas with moderate to high rates of HAV and HBV. These include Africa, the Caribbean, Central America, South America, Mexico, South and Southeast Asia, the Middle East, Eastern Europe, Southern Europe, and the former Soviet Union.²
• Have long-term (chronic) liver disease.
• Use illegal injectable drugs.
• Have anal contact with a sex partner.
• Work in occupations that expose them to viruses, such as some lab workers, people who provide emergency medical assistance, and day care providers.
• Have clotting factor disorders and receive blood products.

How Well It Works

In clinical trials, 1 month after the last dose, 100% of people were immune to hepatitis A, while 99.7% were immune to hepatitis B.¹ But in practice, immunity may not approach these levels. Hepatitis B vaccine usually does not provide immunity for more than 95% to 97% of people.

Immunity to the hepatitis B virus is thought to be lifelong. The hepatitis A vaccine is effective for at least 10 years.¹

Side Effects

In trials of the vaccine, no serious side effects occurred. The most common side effects were those that occur with the individual hepatitis A and B vaccines, such as:

• Soreness at the injection site.
• Headache.
• Fatigue.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Twinrix should not be given to people who are allergic to the contents of the vaccine.

The vaccine has not been tested in pregnant or breast-feeding women, so its safety for these women and their babies is unknown.

To be most effective before travel, two doses need to be given before departure. If only one dose can be given, consider having the individual hepatitis A vaccine instead of one shot of combination vaccine. It may provide better protection against hepatitis A.¹

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