how long is the hepitis a vaccine good for
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.It can also be given in 4 doses, with the initial dose followed by doses at 7 days, 21 to 30 days, and 12 months.mmunity to the hepatitis B virus is thought to be lifelong. The hepatitis A vaccine is effective for at least 25 years in adults and 14 years in children.