The name was created because it is a mixture of two earlier vaccines — Havrix, an inactivated-virus Hepatitis A vaccine, and Engerix-B, a recombinant Hepatitis B vaccine. Twinrix, Havrix and Engerix-B are registered trademarks of GlaxoSmithKline; if the same vaccine is available from others, it will have another name. Twinrix first entered the market in early 1997.
Twinrix can be administered on the same schedule as monovalent Hepatitis B vaccine: at 0- 1- and 6- months. In some circumstances, an accelerated dosing schedule of 0- 7- and 21-to 30- days followed by a booster at 12 months can be used and is believed to have similar efficacy as the traditional schedule.
The CDC reports that clinical trials found the following levels of protection against Hep A and Hep B one month after each dose:
- A: 93.8%, 98.8%, 99.9%
- B: 30.8%, 78.2%, 98.5%
- "FDA approval for a combined hepatitis A and B vaccine". MMWR Morb. Mortal. Wkly. Rep. 50 (37): 806–7. September 2001. PMID 11785573.
- Twinrix Adult Vaccine, SPC from the eMC