• Determine, relative to a 'standard of care' control condition, the efficacy of incentive payments to increase HBV vaccine completion using an accelerated schedule (0,7, and 21 days). [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
  

• Assess the relative cost effectiveness of standard care compared to incentive payments as methods of improving rates of successful vaccine series completion and vaccine-induced immunity [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Identify the correlates of immunity (defined as hepatitis B surface antibody levels greater than 10 mIU/ml [ Time Frame: At baseline and week 12 ] [ Designated as safety issue: No ]
  
• Assess the acceptability of vaccines, including HBV vaccines, barriers to immunisation uptake and willingness to participate in vaccine trials among IDUs [ Time Frame: Baseline( week 0) and week 12 ] [ Designated as safety issue: No ]
  
• Assess hepatitis B-related knowledge in this group [ Time Frame: Baseline( Week 0) and at week 12 ] [ Designated as safety issue: No ]
  

Injecting drug use is the leading exposure category for notifications of newly acquired hepatitis B virus (HBV) infection in Australia. Despite the existence of a safe and efficacious vaccine, hepatitis B coverage remains low among Australian injecting drug users (IDUs) and little is known about attitudes to immunisation, barriers to uptake and willingness to participate in vaccine trials among this group. Candidate vaccines for hepatitis C virus (HCV) and HIV are currently in development and HBV immunisation provides a surrogate for examining strategies to deliver vaccines to this group.

Secondary objectives of this trial are to (i) assess the cost effectiveness of the interventions; (ii) identify the correlates of immunity in this group;(iii)Assess the acceptability of vaccines, including HBV vaccines, barriers to immunisation uptake and willingness to participate in vaccine trials among IDUs:and (iv) Assess hepatitis B−related knowledge in this group.

Research Design: A total of 200 eligible IDUs (those with no history of exposure to or vaccination against HBV) will be recruited and interviewed prior to randomisation on a 1:1 basis (100 per arm) to either the (1) control (standard of care) or (2) incentive conditions. All participants will be offered the 3 dose accelerated vaccine schedule (20ug at 0, 7and 21 days) and will be followed up at week 12.

Inclusion Criteria:

• Aged 16 years and above.
• Injected drugs at least once in the preceding six months.
• No previous hepatitis B vaccination or infection including "don't know"), based on self-report and, where available medical records
• Ability to provide informed consent, to be randomized and attend vaccinations over a period of three weeks and to attend follow-up at 12 weeks post-randomisation.

Exclusion Criteria:

• Evidence of natural or vaccine-induced immunity.
• Previous incomplete or failed vaccinations as identified by self-report
• Serious mental or physical illness or disability likely to impact on capacity to complete the study procedures
• Insufficient English language skills that will impair ability to give informed consent or provide reliable responses to study interviews /questionnaires
• Human Immunodeficiency Virus infection
• Refusal to be vaccinated against Hepatitis B Virus (HBV)