title: Potential impact of vaccination on the hepatitis C virus epidemic in injection drug users.
abstract: BACKGROUND
  Hepatitis C virus (HCV) causes significant morbidity and mortality in injecting drug users (IDU) worldwide. HCV vaccine candidates have shown promise for reducing the infectivity of acute infection and averting chronic infection, yet the impact of varying levels of vaccine efficacy and vaccine delivery strategies on the HCV epidemic in IDU have not been explored.
  
  
  METHODS
  We utilized extensive data on injecting behavior collected in the UFO Study of young IDU in San Francisco to construct a stochastic individual-based model that reflects heterogeneous injecting risk behavior, historical HCV trends, and existing information on viral dynamics and vaccine characteristics.
  
  
  RESULTS
  Our modeled HCV rate closely paralleled observed HCV incidence in San Francisco, with estimated incidence of 59% per person year (ppy) early in the epidemic, and 27% ppy after risk reduction was introduced. Chronic HCV infection, the clinically relevant state of HCV infection that leads to liver disease and hepatocellular cancer, was estimated at 22% ppy (± 3%) early in the epidemic and 14% ppy (± 2%) after risk reduction was introduced. We considered several scenarios, and highlight that a vaccine with 50% to 80% efficacy targeted to high-risk or sero-negative IDU at a high vaccination rate could further reduce chronic HCV incidence in IDU to 2-7% ppy 30 years after its introduction.
  
  
  CONCLUSIONS
  Our results underscore the importance of further efforts to develop both HCV vaccines and optimal systems of delivery to IDU populations.
authors.affiliation: Department of Medicine, University of California, San Francisco, San Francisco, CA 94143-0811, USA. judy.hahn@ucsf.edu
authors.forename: Judith A
authors.initials: JA
authors.lastname: Hahn
authors.forename: Dennis
authors.initials: D
authors.lastname: Wylie
authors.forename: Jesse
authors.initials: J
authors.lastname: Dill
authors.forename: Maria S
authors.initials: MS
authors.lastname: Sanchez
authors.forename: James O
authors.initials: JO
authors.lastname: Lloyd-Smith
authors.forename: Kimberly
authors.initials: K
authors.lastname: Page-Shafer
authors.forename: Wayne M
authors.initials: WM
authors.lastname: Getz
mesh_terms: D003198:Computer Simulation; D016174:Hepacivirus / Q000276:immunology*; D019698:Hepatitis C, Chronic / Q000097:blood / Q000150:complications / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D015995:Prevalence; D012495:San Francisco / Q000453:epidemiology; D013269:Stochastic Processes; D015819:Substance Abuse, Intravenous / Q000150:complications* / Q000523:psychology / Q000821:virology; D014761:Viral Hepatitis Vaccines
chemical_list: D014761:Viral Hepatitis Vaccines
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