Hepatitis A and B vaccine


Twinrix is a vaccine against hepatitis A and hepatitis B, manufactured by GlaxoSmithKline Biologicals. The full generic name is
hepatitis A inactivated & hepatitis B vaccine. Twinrix is administered over three doses.
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 first entered the market in early 1997.
In the United States, Twinrix is approved by the Food and Drug Administration for those aged 18 and older. In some countries outside the United States, notably Canada and Europe, Twinrix is known as Twinrix Adult or Ambirix and a pediatric formulation, called Twinrix Junior or Twinrix Paediatric, is available.

Administration schedule

Routine Twinrix vaccination is administered by intramuscular injection in the deltoid area using a schedule of three separate doses 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 was shown to have similar efficacy as the traditional schedule.

Efficacy

The U.S. Centers for Disease Control and Prevention reports that clinical trials found the following levels of protection against Hepatitis A and Hepatitis B one month after each dose:
GlaxoSmithKline claims that its studies found 70% of subjects had antibodies against hepatitis B a month after just the first dose, however.
Twinrix should not be used for postexposure prophylaxis, because no data are available on the efficacy of combination vaccine for prophylaxis after exposure to HAV.