Wednesday 29 June, 2016 13.00 EDT
Limiting the spread of hepatitis C virus with Treatment as Prevention (TasP)
The idea of Treatment as Prevention, or TasP, has been proposed and is being implemented in some regions as one tool to help control the spread of HIV. An initial part of TasP is offering HIV testing and counselling to help educate people about ways to protect themselves and others from HIV. After counselling, those who test positive can be referred to a healthcare provider so that options for HIV treatment (commonly called ART or HAART) can be discussed. Early treatment helps to maintain the immune system and the health of the person. It also helps to reduce the production of HIV so that the amount of virus in the blood and genital fluids is lessened, reducing the risk of transmission. At the level of a town or urban centre with tens of thousands of people, widespread use of TasP has the potential to help contain and slow the spread of HIV. Reports from British Columbia suggest that TasP works well to restrict the spread of HIV in certain populations, such as people who inject drugs and heterosexual people but less so in men who have sex with men.
Hepatitis C: better drugs, better results
Encouraged by results from TasP in HIV, researchers are also considering TasP as an approach for trying to deal with widespread hepatitis C virus (HCV) infection. Part of the reason for the interest in TasP for HCV is that by 2015, combinations of new, simpler, better-tolerated and interferon-free regimens will be available in many high-income countries. Making regimens that are free of interferon is a major goal for many pharmaceutical companies engaged in HCV drug development. Interferon can cause many side effects including symptoms associated with the flu. However, interferon’s effect on the mental and emotional health of users can be distressing. Side effects associated with this drug can range from irritability, difficulty falling asleep to severe anxiety, anger and depression. These side effects can make it daunting for some HCV-positive people to initiate therapy with interferon and stay on treatment. However, the arrival of several interferon-free regimens over the next few years should greatly remove the fear of interferon as a barrier to starting HCV treatment.
In the time before triple therapy (peginterferon + ribavirin + direct-acting antiviral drug) was available, surveys found that between 56% and 86% of HCV-positive people were willing to consider undergoing therapy with a combination of interferon and ribavirin. It should be expected that once interferon-free regimens become available in 2014, interest and willingness to take such regimens will only increase. This may particularly be the case as regimens become shorter and more powerful (with cure rates around 90% or greater) with fewer pills to take.
Is smaller better?
The course of HCV treatment over the next several years should become shorter, falling to as few as 12 weeks for some people, to longer courses up to 16 or even 24 weeks. The duration of therapy in the future may depend on several factors including the following: the drugs available in different regions, treatment history, strain (or genotype) of HCV, co-infection with HIV, degree of liver damage caused by HCV, and so on. Researchers are conducting clinical trials with a shorter duration of therapy (between six and 10 weeks depending on the regimen being used). However, such trials are being done in very small numbers of people. If it appears that successful treatment can be given in less than 12 weeks, then large trials will be needed to confirm those findings in different populations of HCV-positive people.
A tale of three cities
A team of researchers in Canada, Australia, England and Scotland collaborated on producing a computer model of HCV epidemics in three cities where HCV and injection of street drugs is relatively common:
- Canada – Vancouver
- Australia – Melbourne
- Scotland – Edinburgh
According to their calculations, current, relatively low, rates of HCV treatment will have only a very minimal impact on the future spread of HCV in Melbourne and Vancouver, with a modest impact in Edinburgh.
However, if HCV testing and counselling combined with care and treatment of HCV with emerging interferon-free regimens is implemented on a large scale and maintained for 15 years, the proportion of HCV-positive people in the three cities could fall dramatically—by between 50% and 75%. However, if the expansion of the offer of HCV testing, counselling, care and treatment is delayed beyond 2015 or otherwise limited, TasP will be less effective. A major barrier for the future success of TasP for HCV will be the cost of emerging therapies.
The research team noted that in high-income countries such as Canada, Australia and the U.S. and in regions such as Western Europe, people who share equipment for injecting street drugs generally account for most new HCV infections (up to 80%). Therefore, the researchers suggest that it makes sense to focus on this population for the initial purposes of reducing the spread of HCV.
Limits to current initiatives
In some cities in high-income countries where injecting street drugs is relatively common, authorities deploy programs such as providing clean needles, places where used needles can be deposited and opioid substitution programs (replacing street drugs with prescribed methadone or buprenorphine) accompanied by counselling and referrals for other services. These initiatives can help to reduce the spread of HIV, decrease deaths from overdoses and help people overcome addiction but, according to the researchers, by themselves such programs do not substantially reduce the spread of HCV. This is another reason to explore the potential of TasP for HCV control.
Based on the study team’s calculations, there are several possible outcomes for the spread of HCV, as follows:
Business as usual
If there was no massive expansion of HCV testing and treatment efforts and new, potent interferon-free regimens were gradually introduced, researchers predict the following occurring over the next 15 years:
- Edinburgh – 26% fewer HCV infections
- Melbourne – less than a 2% decrease in new HCV infections
- Vancouver – less than a 2% decrease in new HCV infections
The reason for the lesser outcomes for Melbourne and Vancouver is that those cities have a more concentrated HCV epidemic than Edinburgh.
A bigger bang
To have a greater impact on the spread of HCV in Melbourne and Vancouver, the research team calculated that intensive programs, such as making the option of an HCV test more available, followed by counselling and swift referral to care and treatment would be needed.
For instance, to reduce the proportion of HCV-positive people in the three cities by over 50% over the next 15 years, treatment rates would have to increase as follows:
- Edinburgh – double the number of people taking HCV treatment
- Melbourne – 13-fold increase in the number of people taking HCV treatment
- Vancouver – 15-fold increase in the number of people taking HCV treatment
To reduce the proportion of people with HCV even further, more intensive treatment programs would be necessary.
Researchers conservatively estimate that investments of about $50 million per year in Melbourne and Vancouver, and about $3 million per year in Edinburgh will be needed to cut the proportion of HCV-positive people by 50%. These costs are based on estimates of the emerging therapies costing formularies about $50,000 per person. That may be the case with one new direct-acting antiviral (DAA) + interferon + ribavirin. However, by 2015, with several new drugs having been licensed, doctors and patients will likely want to use two or more powerful DAAs simultaneously, possibly displacing the more unpleasant and less effective interferon + ribavirin.
Indeed, interferon-free regimens that are highly effective against a broad range of HCV genotypes are likely to be costly—a pricing trend seen in emerging and increasingly effective therapies for cancer. Unless manufacturers and regional drug formularies (which subsidize access to treatment for many illnesses) can reach agreement about costs, TasP for HCV may be difficult to achieve, even in high-income countries.
Other support needed
To expand the population of HCV-positive people who can successfully navigate a course of treatment, Australian researchers suggest that potential HCV TasP programs need to explore at least the following elements:
- pill boxes
- electronic reminders about pill-taking
- peer counselling
- case management
- nurse-led counselling
- integrating HCV treatment into existing health services that may be found in places such as prisons, as part of opioid substitution programs and in primary care clinics
This last point is interesting because clearly HCV treatment needs to be expanded to populations with high rates of HCV. However, unless existing health services are well resourced to deal with the influx of large numbers of new patients, TasP is going to encounter difficulties.
Treating the whole person
There are related matters that were not mentioned by the mathematical modellers. For instance, health systems may need to become more adaptable and change to meet the needs of more people with HCV as they come forward for treatment. This may mean that governments fund more community-based treatment clinics that provide an array of services related to the complex health and psychosocial needs of people with HCV and not just focus on HCV treatment.
Underpinning the addiction(s)
Issues that should be addressed at such clinics, and indeed future models of HCV TasP rollout, are the underlying emotional concerns that caused some people to attempt to relieve distress by injecting street drugs in the first place. Thus, treatment of mental health conditions—including anxiety, depression, bipolar illness, psychosis and so on—needs to be part of an integrated approach to TasP. Educating people about healthy ways of coping with challenging situations can also be helpful. Also, because of poor life circumstances, some people who inject street drugs will need prolonged counselling for post-traumatic stress disorder.
Although potential TasP programs assume that courses of HCV treatment will be relatively short, recovery from years of addiction does not occur in a few weeks. TasP programs will need to help people who are recovering from HCV gain an understanding of the psychological drivers of their addiction, perhaps teach basic life skills and, for some people, reintegration into wider society. If attention is not paid to addiction-related issues, it is possible that some people who are initially cured of HCV can have their addiction recur, become reinfected and/or infected with other germs, and/or develop different addictions in the future.
Looking at large numbers of people – population level
In another study, researchers in Australia also examined the potential of TasP. In their study, the researchers raised questions about the goals of health policy planners. For instance, if the main goal of policy planners is to reduce the spread of HCV, then Australian researchers made this statement: “the majority of therapy should be allocated to [people who are currently injecting street drugs].”
Looking at the individual level rather than the population level
However, the same group of Australian researchers also notes: “In the short term, HCV treatment may have the greatest impact on [HCV-related complications and death] if targeted towards people who inject drugs who have already been infected with HCV for many years with the greatest risk of disease progression and death.”
A fine balance
In Canada and other high-income countries, the vast majority of care and treatment for HCV is and will be state funded. Therefore, an ethical and balanced approach to the distribution of emerging treatments—between population level and individual level goals—will be needed as HCV test-and-treat strategies are expanded.
—Sean R. Hosein
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