The role of a hepatitis C virus vaccine: modelling the benefits alongside direct-acting antiviral treatments.
BACKGROUND
Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination models require a combination of highly effective HCV treatment and harm reduction, but high treatment costs make such strategies prohibitively expensive. Vaccines should play a key role in elimination but their best use alongside treatments is unclear. For three vaccines with different efficacies we used a mathematical model to estimate the additional reduction in HCV prevalence when vaccinating after treatment; and to identify in which settings vaccines could most effectively reduce the number of treatments required to achieve fixed reductions in HCV prevalence among people who inject drugs (PWID).


METHODS
A deterministic model of HCV transmission among PWID was calibrated for settings with 25, 50 and 75% chronic HCV prevalence among PWID, stratified by high-risk or low-risk PWID. For vaccines with 30, 60 or 90% efficacies, different rates of treatment and vaccination were introduced. We compared prevalence reductions achieved by vaccinating after treatment to prevent reinfection and vaccinating independently of treatment history in the community; and by allocating treatments and vaccinations to specific risk groups and proportionally across risk groups.


RESULTS
Vaccinating after treatment was minimally different to vaccinating independently of treatment history, and allocating treatments and vaccinations to specific risk groups was minimally different to allocating them proportionally across risk groups. Vaccines with 30 or 60% efficacy provided greater additional prevalence reduction per vaccination in a setting with 75% chronic HCV prevalence among PWID than a 90% efficacious vaccine in settings with 25 or 50% chronic HCV prevalence among PWID.


CONCLUSIONS
Vaccinating after treatment is an effective and practical method of administration. In settings with high chronic HCV prevalence among PWID, even modest coverage with a low-efficacy vaccine could provide significant additional prevalence reduction beyond treatment alone, and would likely reduce the cost of achieving prevalence reduction targets.
Centre for Population Health, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, 3004, Australia. nick.scott@burnet.edu.au.|Department of Epidemiology and Preventive Medicine, Monash University, Clayton, VIC, 3800, Australia. nick.scott@burnet.edu.au.
Nick
N
Scott
Centre for Population Health, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, 3004, Australia. Emma.McBryde@mh.org.au.|Doherty Institute for Infection and Immunity, 792 Elizabeth Street, Melbourne, VIC, 3000, Australia. Emma.McBryde@mh.org.au.|Department of Medicine, The University of Melbourne, Parkville, VIC, 3050, Australia. Emma.McBryde@mh.org.au.|Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, QLD, 4811, Australia. Emma.McBryde@mh.org.au.
Emma
E
McBryde
School of Social and Community Medicine, University of Bristol, Bristol, UK. Peter.Vickerman@bristol.ac.uk.|Department for Global Health and Development, London School of Hygiene and Tropical Medicine, London, UK. Peter.Vickerman@bristol.ac.uk.
Peter
P
Vickerman
School of Social and Community Medicine, University of Bristol, Bristol, UK. Natasha.Martin@bristol.ac.uk.|Division of Global Public Health, University of California, San Diego, USA. Natasha.Martin@bristol.ac.uk.
Natasha K
NK
Martin
School of Social and Community Medicine, University of Bristol, Bristol, UK. Jack.Stone@bristol.ac.uk.
Jack
J
Stone
Centre for Biomedical Research, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, 3004, Australia. hdrummer@burnet.edu.au.|Department of Microbiology, Monash University, Clayton, VIC, 3800, Australia. hdrummer@burnet.edu.au.|Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, 3000, Australia. hdrummer@burnet.edu.au.
Heidi
H
Drummer
Centre for Population Health, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, 3004, Australia. Hellard@burnet.edu.au.
Margaret
M
Hellard
D000998:Antiviral Agents / Q000627:therapeutic use*; D017048:Health Care Costs; D016174:Hepacivirus / Q000187:drug effects; D019698:Hepatitis C, Chronic / Q000188:drug therapy / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D008962:Models, Theoretical; D015995:Prevalence; D015819:Substance Abuse, Intravenous / Q000150:complications / Q000628:therapy; D014611:Vaccination / Q000191:economics / Q000379:methods; D014761:Viral Hepatitis Vaccines / Q000191:economics / Q000627:therapeutic use
D000998:Antiviral Agents; D014761:Viral Hepatitis Vaccines