hepatitis a and b shots
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.