title: The Potential Impact of a Hepatitis C Vaccine for People Who Inject Drugs: Is a Vaccine Needed in the Age of Direct-Acting Antivirals?
abstract: OBJECTIVE
  The advent of highly effective hepatitis C (HCV) treatments has questioned the need for a vaccine to control HCV amongst people who inject drugs (PWID). However, high treatment costs and ongoing reinfection risk suggest it could still play a role. We compared the impact of HCV vaccination amongst PWID against providing HCV treatment.
  
  
  METHODS
  Dynamic HCV vaccination and treatment models among PWID were used to determine the vaccination and treatment rates required to reduce chronic HCV prevalence or incidence in the UK over 20 or 40 years. Projections considered a low (50% protection for 5 years), moderate (70% protection for 10 years) or high (90% protection for 20 years) efficacy vaccine. Sensitivities to various parameters were examined.
  
  
  RESULTS
  To halve chronic HCV prevalence over 40 years, the low, moderate and high efficacy vaccines required annual vaccination rates (coverage after 20 years) of 162 (72%), 77 (56%) and 44 (38%) per 1000 PWID, respectively. These vaccination rates were 16, 7.6 and 4.4 times greater than corresponding treatment rates. To halve prevalence over 20 years nearly doubled these vaccination rates (moderate and high efficacy vaccines only) and the vaccination-to-treatment ratio increased by 20%. For all scenarios considered, required annual vaccination rates and vaccination-to-treatment ratios were at least a third lower to reduce incidence than prevalence. Baseline HCV prevalence had little effect on the vaccine's impact on prevalence or incidence, but substantially affected the vaccination-to-treatment ratios. Behavioural risk heterogeneity only had an effect if we assumed no transitions between high and low risk states and vaccinations were targeted or if PWID were high risk for their first year.
  
  
  CONCLUSIONS
  Achievable coverage levels of a low efficacy prophylactic HCV vaccine could greatly reduce HCV transmission amongst PWID. Current high treatment costs ensure vaccination could still be an important intervention option.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Jack
authors.initials: J
authors.lastname: Stone
authors.affiliation: Division of Global Public Health, University of California San Diego, La Jolla, United States of America.|School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Natasha K
authors.initials: NK
authors.lastname: Martin
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Hickman
authors.affiliation: Centre for Population Health, Burnet Institute, Melbourne, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Hellard
authors.affiliation: Centre for Population Health, Burnet Institute, Melbourne, Australia.
authors.forename: Nick
authors.initials: N
authors.lastname: Scott
authors.affiliation: Centre for Population Health, Burnet Institute, Melbourne, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: McBryde
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia.
authors.forename: Heidi
authors.initials: H
authors.lastname: Drummer
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Vickerman
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use*; D016174:Hepacivirus / Q000187:drug effects; D019698:Hepatitis C, Chronic / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D008962:Models, Theoretical; D015995:Prevalence; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*; D013997:Time Factors; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology; D014611:Vaccination / Q000379:methods*; D014761:Viral Hepatitis Vaccines / Q000191:economics / Q000627:therapeutic use*
chemical_list: D000998:Antiviral Agents; D014761:Viral Hepatitis Vaccines