Twinrix (GSK) is an inactivated combination vaccine containing both hepatitis A virus (HAV) and HBV antigens. The vaccine contains 720 EL.U. of hepatitis A antigen (half of the Havrix adult dose) and 20 mcg of hepatitis B antigen (the full Engerix-B adult dose). In the United States, Twinrix is licensed for use in people who are age 18 years or older. It can be administered to people who are at risk for hepatitis A and who are recommended to receive hepatitis B vaccination, such as certain international travelers, people with chronic liver disease, men who have sex with men, people who use drugs, or to people who want to be immune to both diseases.
A standard Twinrix series consists of 3 doses given intramuscularly on a 0, 1, and 6 month schedule.
In March 2007, the FDA approved a 4-dose schedule for Twinrix. It consists of 3 doses given within 3 weeks, followed by a booster dose at 12 months (0, 7 days, 21 to 30 days, and 12 months). The 4-dose schedule could benefit individuals needing rapid protection from hepatitis A and hepatitis B, such as some people traveling imminently. Twinrix cannot be used for post-exposure prophylaxis.