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This is a vaccine that protects against hepatitis A and B


Active ingredients:

Inactivated hepatitis A virus and recombinant hepatitis B surface antigen (a protein outside of the virus)

The hepatitis B surface antigens are recombinant proteins: the information for how to make these proteins is inserted into the genome of Saccharomyces cerevisiae, which is yeast. The yeast produce the proteins, which are used as the active ingredients in the vaccine. The proteins act as antigens that allow the immune system to make antibodies against HPV. Because these are proteins, not whole bacteria, you cannot get HPV from the vaccine.


This vaccine uses MRC-5 cells to grow hepatitis A virus for the vaccine. These cells are considered safe. This vaccine may contain traces of proteins from MRC-5 cells.

In addition, this vaccine contains a small amount of yeast because it is used to produce the hepatitis B surface antigen, but even people with yeast allergies can safely receive this vaccine. If you have concerns about a yeast allergy (or an allergy to any other ingredient), please contact your doctor.

For several ingredients in this vaccine, the amount was not given. However, this vaccine is derived from two other vaccines (Havrix and Engerix-B), so the amounts listed for those ingredients below are taken from the other inserts. The amounts should be almost identical because Twinrix is derived from these vaccines.

Inactive ingredients:
Amounts are based on a 1 mL dose

Adjuvants: strengthen the immune response to the vaccine

Antibiotics: used to prevent contamination during the manufacturing process

Salts: help maintain the stability and pH of the vaccine


Relevant Terms

  • Antibiotics: substances that kill bacteria or prevent them from dividing. Antibiotics are used in some vaccines to prevent contamination during the manufacturing process.

  • Genome: all of the genetic information in a cell.

  • Emulsifier: a substance that helps to keep the ingredients mixed together

  • MRC-5 cells: This is a human cell line that is used to help grow active ingredients for vaccines

  • pH: a measure of how acidic or basic a solution is. The scale ranges from 0 (very acidic) to 14 (very basic). A pH of 7 is neutral.

Relevant Terms


Last updated: Apr. 8, 2023

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