The Twinrix vaccination combines the Hepatitis A & Hepatitis B vaccinations so that travelers can get vaccinated against both viruses at the same time. It is available for people 18years or older. This, too, is a series of 3 injections, given at day 1, one month later and then 6months after the first injection. If the series is not completed by the time of travel, there is some degree of immunization after the first two doses; however, one is not considered fully immunized until the series is finished. For travelers whose time is of the essence, there is an accelerated schedule option. This series consists of 4 injections, given at day 1, 7, and 21 followed by a booster dose at 12 months.