Treatment for prevention for hepatitis C in French drug users could cut HCV prevalence by two-thirds in 10 years

A combination of increased testing, improved linkage to care and treatment immediately after diagnosis with interferon-free regimens has the potential to substantially reduce the incidence and prevalence of hepatitis C virus (HCV) among people who inject drugs in France over the next 10 years, as well as reducing the burden of disease arising from cirrhosis over 40 years, according to a study presented at the 49th Annual Meeting of the European Association for the Study of the Liver (EASL) in London on Friday.

Using treatment to reduce the rate of new infections is already an established aim of antiretroviral treatment for HIV infection, although the full potential of the strategy is still being tested in large studies.

Several research groups have developed models of the impact of hepatitis C treatment on new infections, focusing in particular on HCV incidence among people who inject drugs, where rates of transmission continue to be high in many settings.

Injecting drug use is an important vector for HCV transmission because the sharing of needles and injecting equipment is a highly efficient means of passing the virus from one person to another. HCV may survive for several weeks in microscopic particles of dried blood in needles, syringes and other paraphernalia used to prepare drugs for injecting.

Addressing the continuing high incidence of hepatitis C among people who inject drugs also has the potential to limit subsequent onward transmission where lack of medical precautions leads to infections during medical and dental procedures.

Investigators developed a mathematical model to simulate the rates of HCV transmission among 10,000 injecting drug users in France over a ten-year period. HCV prevalence at baseline was 43%.

The impact of seven prevention strategies on prevalence and incidence were simulated.

1. Current cascade of care with introduction of direct-acting antivirals (DAAs) and cure rates between 63 and 72% depending on genotype.
2. Prompter diagnosis, within six months of infection but moderately improved cure rate (81%).
3. Improved linkage to care but moderately improved cure rate (81%).
4. Improved linkage to care and testing but moderately improved cure rate (81%).
5. Improved adherence to treatment but high loss to follow-up (14% per year, 90% cure rate).
6. Earlier initiation of treatment but high loss to follow-up (14% loss to follow-up, 81% cure rate).
7. Combination of improved linkage to care/testing, adherence and earlier treatment, combining diagnosis of HCV within six months of acquisition, immediate linkage to care, low loss to follow-up, treatment of all diagnosed people and a 90% cure rate.

Three different scenarios were considered regarding the average number of injecting partners: three, six or fifteen.

Results of the model suggested the implementation of strategies 1-5 would have a similar impact on the French HCV epidemic among people who inject drugs. With these strategies, prevalence would be between 28 and 33%, with incidence between 0.016-0.024. Complications due to cirrhosis – the largest cost to the health system – would increase by 21% over the next 40 years without the introduction of interferon-free regimens, but fall by 27% if the optimal package of testing, linkage to care and treatment was implemented.

Earlier treatment at fibrosis stages F0-F1 was shown to have a much bigger impact on the epidemic, reducing prevalence to between 14 and 15% and incidence to 0.008-0.012.

The combination strategy had the most profound effect, with prevalence to falling to 9 to 10% and incidence to 0.006-0.008.

“With DAA-containing regimens, earlier treatment will have an important impact on the HCV transmission among injecting drug users in France, which will be even more important if implemented in combination with ambitious testing, linkage and adherence to care/treatment interventions.” conclude the authors. However, they caution “these interventions will still not stop transmission, underlining the importance of their combination with risk reduction programmes.”

The findings also indicate the importance of high levels of performance at each stage in the 'treatment cascade'.  Substantial reductions in transmission were achieved only with very early diagnosis and immediate treatment, implying the need for 'seek and treat' outreach programmes among people who inject drugs.