Strategies to reduce HCV disease burden and HCV transmission need different models, as what works for end-stage liver disease may not work for HCV prevalence: a comment on the results presented in JVH Special Issue

Hepatitis C virus treatment as prevention in people who inject drugs: testing the evidence

PURPOSE OF REVIEW

The majority of hepatitis C virus (HCV) infections in the United Kingdom and many developing countries were acquired through injecting. New clinical guidance suggests that HCV treatment should be offered to people with a transmission risk - such as people who inject drugs (PWID) - irrespective of severity of liver disease. We consider the strength of the evidence base and potential problems in evaluating HCV treatment as prevention among PWID.

RECENT FINDINGS

There is good theoretical evidence from dynamic models that HCV treatment for PWID could reduce HCV chronic prevalence and incidence among PWID. Economic evaluations from high-income settings have suggested HCV treatment for PWID is cost-effective, and that in many settings HCV treatment of PWID could be more cost-effective than treating those at an equivalent stage with no ongoing transmission risk. Epidemiological studies of older interferon treatments have suggested that PWID can achieve similar treatment outcomes to other patient groups treated for chronic HCV. Impact and cost-effectiveness of HCV treatment is driven by the potential 'prevention benefit' of treating PWID. Model projections suggest that more future infections, end stage liver disease, and HCV-related deaths will be averted than lost through reinfection of PWID treated successfully for HCV. However, there is to date no empirical evidence from trials or observational studies that test the model projections and 'prevention benefit' hypothesis. In part this is because of uncertainty in the evidence base but also there is unlikely to have been a change in HCV prevalence due to HCV treatment because PWID HCV treatment rates historically in most sites have been low, and any scale-up and switch to the new direct acting antiviral has not yet occurred. There are a number of key uncertainties in the data available on PWID that need to be improved and addressed to evaluate treatment as prevention. These include estimates of the prevalence of PWID, measurements of HCV chronic prevalence and incidence among PWID, and how to interpret reinfection rates as potential outcome measures.

SUMMARY

Eliminating HCV through scaling up treatment is a theoretical possibility. But empirical data are required to demonstrate that HCV treatment can reduce HCV transmission, which will require an improved evidence base and analytic framework for measuring PWID and HCV prevalence.

Estimates on HCV disease burden worldwide - filling the gaps

Hepatitis C is caused by infection with the hepatitis C virus (HCV) and represents a major global health burden. Persistent HCV infection can lead to progressive liver disease with the development of liver cirrhosis and hepatocellular carcinoma, possibly accounting for up to 0.5 million deaths every year. Treatment of HCV infection is undergoing a profound and radical change. As new treatments are extremely safe and effective, there are virtually no medical reasons to withhold therapy. Yet, the new therapies are expensive. As resources are limited, solid data to estimate the disease burden caused by HCV are urgently needed. Epidemiology data and disease burden analyses for 16 countries are presented. For almost all countries, the peak of HCV-related cirrhosis, hepatocellular carcinoma and liver-related death is a decade or more away. However, a surprising heterogeneity in country-specific HCV-associated disease burden exists. Also, HCV diagnosis and treatment uptake varied markedly between countries. A consistent finding was that a reduction of HCV liver-related mortality is dependent on access to therapy. Increasing efficacy of therapy alone with a constant numbers of treatments will not have a major impact on the HCV-related disease burden. The data presented here should inform public health policy and help drive advocacy for enhanced strategic investment and action. HCV kills patients, and the disease burden will continue to rise in most countries unless action is taken soon. Chronic HCV is a curable infection and a reversible liver disease. Fortunately, the tools to eliminate HCV are now available.