- Category: Injection Drug Use
- Published on Sunday, 13 April 2014 00:00
- Written by Keith Alcorn
A combination of increased testing, improved linkage to care, and earlier treatment with interferon-free regimens has the potential to substantially reduce the incidence and prevalence of hepatitis C 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 EASL International Liver Congress (EASL 2014) last week in London.
Using treatment to reduce the rate of new infections is already an established aim of antiretroviral treatment for HIV, although the full potential of the strategy is still being tested in large studies.
Several research groups have likewise 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.
Injection drug use is an important vector for HCV transmission because the sharing of needles and other 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 injection drug users in France over a 10-year period. HCV prevalence at baseline was 43%. They simulated the impact on HCV prevalence and incidence based on 7 prevention scenarios:
1. Current cascade of care with introduction of direct acting antiviral agents (DAAs) and cure rates between 63%-72% depending on HCV genotype.
2. Prompter diagnosis, within 6 months of infection, with moderately improved cure rate (81%).
3. Improved linkage to care with moderately improved cure rate (81%).
4. Improved linkage to care and increased testing with moderately improved cure rate (81%).
5. Improved adherence to treatment but high loss to follow-up (14% loss to follow-up, 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 and testing, improved adherence, and earlier treatment, combining diagnosis within 6 months of HCV acquisition, immediate linkage to care, low loss to follow-up, treatment of all diagnosed people, and a 90% cure rate.
In addition, 3 different scenarios were considered regarding the average number of injecting partners: 3, 6, or 15.
Results of the model suggested that the implementation of strategies 1 through 5 would have a similar impact on the French hepatitis C epidemic among injection drug users. With these strategies, prevalence would be between 28%-33%, with incidence between 0.016-0.024.
Complications due to liver 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 would 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%-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," concluded the authors. However, they caution, "these interventions will still not stop transmission, underlining the importance of their combination with risk reduction programs."
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 programs among people who inject drugs.
A Cousien, VC Tran, M Jauffret-Roustide, et al. Impact of New DAA-containing Regimens on HCV Transmission among Injecting Drug Users (IDUs): a Model-based Analysis (ANRS 12376). 49thEuropean Association for the Study of the Liver International Liver Congress (EASL 2014). London, April 9-13, 2014. Abstract O89.