PWID/PWUD are at high risk for infection with the hepatitis viruses, particularly HCV and HBV. They will be systematically screened for Hepatitis B (after informed consent) and those who resulted as a negative will be vaccinated for Hepatitis B. HBV vaccination is given to PWID/PWUD and AHRN health-care workers. Due to chaotic lifestyles, accelerated vaccination schedule of 0, 7 and 21 days is used. Double-dose regimen will be given in the context of HIV infection.