Articles tagged as "Injecting drug use and HIV prevention"

Predicting the impact of treatment as prevention for people who inject drugs

Treatment as prevention among injecting drug users; extrapolating from the Amsterdam cohort study.

de Vos AS, Prins M, Coutinho RA, van der Helm JJ, Kretzschmar ME. AIDS 2014 Jan 7. [Epub ahead of print]

Objective: To determine the potential of treatment as prevention for reducing HIV incidence among injecting drug users (IDU).

Methods: Transmission dynamics of HIV as influenced by cART uptake and demographic changes were studied using an individual-based model. Parameters were based on data of the Amsterdam Cohort Study, and counterfactual treatment scenarios were examined for this city. Demography of the modeled population was also varied to allow for more general conclusions.

Results: We estimated that over the complete HIV epidemic among IDU in Amsterdam the historic use of cART has led to only 2% less incidence. As individuals were treated from low CD4-counts, their decreased infectiousness was offset by increased infectious lifetime. Large reduction in incidence could result from a test and immediate treat strategy, with elimination of HIV occurring when the average time from infection to starting treatment was less than 2 months. However, substantial proportions of new infections were prevented only if the test and treat intervention was implemented within the first few years after HIV-epidemic onset, especially for a declining IDU population. Ignoring heterogeneity in risk-behavior led to overly optimistic expectations of the prevention effects of treatment. In general, treatment led to much greater reduction in incidence compared with stopping HIV+ IDU from lending out syringes.

Conclusion: A test and immediate treat strategy for HIV among IDU could lead to great reductions in incidence. To fully eliminate the spread of HIV, treatment as prevention should be combined with other interventions, with behavioral intervention directed at those not yet HIV infected.

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Editor’s notes: Treatment as prevention has been shown to substantially reduce the risk of sexual HIV transmission, and modelling has been used to estimate the impact of treatment as prevention in epidemics driven by sexual spread. Much less attention has been paid to the potential for treatment as prevention to reduce transmission amongst people who inject drugs, who account for 10% of people living with HIV globally. In this modelling study, the authors use a mathematical model of HIV transmission amongst people who inject drugs in Amsterdam to estimate the impact that treatment has had in this setting. The authors then estimate the impact that different testing and treatment strategies could have had in this setting and in other settings with increasing or stable populations of people who inject drugs. Their findings suggest that treatment has had little impact on incidence among people who inject drugs in Amsterdam.  This was partly due to late treatment, declining HIV prevalence and a declining population of people who inject drugs. They find that more frequent testing, coupled with earlier treatment could have a large impact if it is introduced soon after the introduction of HIV into populations of people who inject drugs, particularly if the population is stable or increasing in size. This could be relevant in places where injecting drug use is becoming more common, or in settings where HIV has only recently begun to be spread through injecting drug use. The authors do highlight however, that treatment as prevention alone is unlikely to lead to elimination of HIV, and that harm reduction strategies remain important.     

Europe
Netherlands
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Successful integration of HIV and TB care into a methadone programme

Lessons from Tanzania on the integration of HIV and tuberculosis treatments into methadone assisted treatment.

Bruce RD, Lambdin B, Chang O, Masao F, Mbwambo J, Mteza I, Nyandindi C, Zamudio-Haas S, Buma D, Dunbar MS, Kilonzo G. Int J Drug Policy 2014 Jan;25(1):22-5. doi: 10.1016/j.drugpo.2013.09.005. Epub 2013 Sep 19.

To successfully address HIV and TB in the world, we must address the healthcare needs of key populations, such as drug users, and we must do this urgently. Currently in Tanzania, as in many countries, the care for these medical disorders is separated into disease specific clinical environments. Our consortium began working to integrate HIV and TB clinical services into the methadone program in Dar es Salaam, Tanzania. We present the key lessons learned in this process of integration and the importance of integrating HIV/TB into the methadone program, which serves as a critical anchor for adherence to clinical services. Integrated healthcare for people who use drugs is clearly a long-term goal and different health systems will progress upon this continuum at different rates. What is clear is that every health system that interacts with drug users must aspire to achieve some level of integrated healthcare if the incidence rates of HIV and TB are to decline.

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Editor’s notes: The prevalence of injecting drug use is unknown in many resource-limited settings, but is increasing in some African countries. Harm reduction programmes for people who inject drugs are generally less well-developed in resource-limited settings, and, where available, such programmes are usually delivered separately from HIV care services. People living with HIV who inject drugs are at high risk of tuberculosis. Moreover, concurrent treatment for all three conditions is complicated, with potential for drug-drug interactions. Integration of opiate substitution therapy with treatment for HIV and, when necessary, tuberculosis treatment, has many advantages for service users.

This article describes lessons learned from a case study of successful integration of HIV and tuberculosis treatment into a methadone programme in Dar es Salaam, United Republic of Tanzania. Initially, HIV testing was offered to clients attending for methadone: around one-third were found to be HIV-positive. Antiretroviral treatment was made available as directly-observed therapy from the pharmacist dispensing daily methadone. Subsequently, screening for tuberculosis and directly-observed tuberculosis treatment were introduced. This is an encouraging example of patient-centred, integrated care.

Africa
United Republic of Tanzania
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Female sex work in Central Asia: a neglected population for research and intervention

HIV among female sex workers in the Central Asian Republics, Afghanistan, and Mongolia: contexts and convergence with drug use.

Baral S, Todd CS, Aumakhan B, Lloyd J, Delegchoimbol A, Sabin K. Drug Alcohol Depend. 2013 Nov;132 Suppl 1:S13-6. doi: 10.1016/j.drugalcdep.2013.07.004. Epub 2013 Aug 14.

Background: Central Asia is culturally and demographically diverse, both between and within its respective countries. That diversity is represented in the range of individual, network, community, and structural risks for female sex workers (FSWs) regionally. FSWs have several risk factors for HIV acquisition and transmission including behavioral, biological, and structural risk factors. Across Central Asia, sexual risks have become conflated with risks associated with injection and non-injection illicit drug use.

Methods: Peer-reviewed literature databases and gray literature were searched for articles on sex work in Central Asia. The medical subject heading (MeSH) of "sex work" was cross-referenced with terms associated with Uzbekistan, Tajikistan, Turkmenistan, Kazakhstan, Kyrgyzstan, Mongolia, and Afghanistan.

Results: HIV prevalence data for FSWs suggest sustained or increasing prevalence in the region. There are increasing data directly linking HIV among FSWs to injection drug use; odds of HIV are up to 20 times higher among FSWs reporting injecting drug use. Though injecting drug use among FSWs is rare in some settings, recreational drugs and alcohol use limits other risk reduction behaviors, such as condom use.

Conclusions: The Central Asian HIV epidemic has traditionally been assumed to be driven nearly exclusively by drug use, resulting in surveillance systems focused on parenteral transmission. The reviewed data highlight limited attention to characterizing the burden of HIV and risk factors for HIV acquisition and transmission among FSWs who use drugs. Moving forward will require enhanced HIV surveillance and research to inform HIV prevention approaches to address all levels of HIV risks affecting FSWs in Central Asia.

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Editor’s notes: This paper summarises available data on HIV prevalence among female sex workers in Central Asia. The many gaps in information are striking – with data on HIV prevalence being available for only three of the seven countries reviewed, data on HIV among injecting female sex workers (FSW) available from three countries, and data on HIV among non-injecting female sex workers being available from one country only. The most detailed data came from Kyrgyzstan, where, as would be expected, injecting female sex workers were at greatest risk of HIV, and also had very high levels of hepatitis C infection. The findings highlight the need to expand surveillance systems in the region. Doing so will lead to better geographical coverage, and also to obtain more routinely compiled information on the extent of sex work and the prevalence of HIV infection among injecting and non-injecting sex workers. The high risk of HIV and hepatitis C infection among injecting FSW highlight also the importance of programmes for sex workers who inject drugs.   

Asia
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More evidence on men who have sex with men in Central Asia needed

Uncovering the epidemic of HIV among men who have sex with men in Central Asia.

Wirtz AL, Kirey A, Peryskina A, Houdart F, Beyrer C. Drug Alcohol Depend. 2013 Nov;132 Suppl 1:S17-24. doi: 10.1016/j.drugalcdep.2013.06.031. Epub 2013 Jul 29.

Background: Research among people who inject drugs (PWID) in Central Asia has described same sex behavior among male PWID and may be associated with HIV and other infections. Little is known about the population of men who have sex with men (MSM) and the burden of HIV among MSM in Central Asian countries.

Methods: We conducted a comprehensive search of peer-reviewed publications and gray literature on MSM and HIV in the region. Search strategies included terms for MSM combined with five Central Asian countries and neighbors, including Mongolia, Afghanistan, and Xinjiang Province, China.

Results: 230 sources were identified with 43 eligible for inclusion: 12 provided HIV prevalence and population size estimates for MSM, none provided incidence estimates, and no publications for Turkmenistan were identified. National reports estimate HIV prevalence among MSM to range from 1 to 2% in Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, Xinjiang, to 10% in Mongolia. Biobehavioral studies estimated HIV prevalence at 0.4% in Afghanistan and 20.2% in Kazakhstan. Sexual identities and behaviors vary across countries. Injection drug use was relatively low among MSM (<5% for most). Non-injection drugs, alcohol use prior to sex, and binge drinking were more common and potentially associated with violence. Criminalization of homosexuality (Afghanistan, Uzbekistan, and Turkmenistan) and stigma has limited research and HIV prevention.

Conclusion: Improved understanding of risks, including potential linkages between sexual exposures and substance use, among MSM are important for response. The little known about HIV among MSM in Central Asia speaks to the urgency of improvements in HIV research, prevention, and care.

Abstract access

Editor’s notes: In Central Asia, the HIV epidemic has historically been characterised as primarily being driven by injecting drug use. However, this is an over-simplification, and research with people who inject drugs is starting to show that some men who inject drugs, also have sex with men. This review compiled existing evidence about HIV among men who have sex with men (MSM) in the region, from both the academic and grey literature. The paper is important, both because of the insights that the findings provide, as well as because of the large gaps in data that it illustrates. Currently there is extremely limited data that can be used to characterise the burden of HIV and risk factors for HIV acquisition and transmission among MSM, including men who use drugs. This provides an incomplete picture of the HIV epidemic in the region. Stronger evidence about the broader range of vulnerable populations, and the interactions and overlapping of risk behaviours, is needed.  This is necessary to better understand and characterise the epidemic in each country in the region; and to help shape a more effective response.  

Asia
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Intersecting epidemics: violence, drug use and sex work

Female Sex Workers in Three Cities in Russia: HIV Prevalence, Risk Factors and Experience with Targeted HIV Prevention.

Decker MR, Wirtz AL, Moguilnyi V, Peryshkina A, Ostrovskaya M, Nikita M, Kuznetzova J, Beyrer C. AIDS Behav. 2013 Aug 9. [Epub ahead of print]

Within Eastern Europe/Central Asia's expanding HIV epidemic, relatively little is known about female sex workers (FSWs). Using mixed methods, we report on sex work context, HIV prevalence and contextual risk factors, and exposure to FSW-targeted prevention services among FSWs in Kazan, Krasnoyarsk, and Tomsk, Russia. Following a qualitative phase, FSWs (n = 754) were recruited via respondent-driven sampling for a cross-sectional survey with HIV screening in 2011. HIV was prevalent (3.9 %). In adjusted analyses, significant risk factors included injection drug use (IDU; AOR 5.85, 95 % CI 2.47, 14.43), client-perpetrated physical violence (AOR 2.52, 95 % CI 1.41, 4.51), and client-perpetrated sexual violence (vaginal AOR 3.77, 95 % CI 1.73, 8.22; anal AOR 4.80, 95 % CI 1.89, 12.19). FSW-targeted programming (reported by 75 %) was described as highly valuable, providing free, anonymous, and non-stigmatizing care. Findings confirm FSWs as a core HIV risk population in Russia, and demonstrate the need to support FSW-oriented HIV services. Such efforts should address violence against FSWs.

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Editor’s notes: Previous epidemiological studies have focussed on measuring HIV and sexually transmitted infections on sampling populations of people who inject drugs and who also exchange sex. This is one of the first studies to sample female sex workers (FSWs) in Russia. The study suggests that HIV transmission among this population remains highly associated with injecting drug use. It is also one of the first studies from the region to quantify the experience of both sexual and physical violence among female sex workers and measure its effect on HIV prevalence. Findings demonstrate that experience of sexual violence from clients is associated with increased likelihood of HIV infection. It also shows that physical violence from clients may, through more indirect routes, increase likelihood of being infected with HIV. This supports other evidence that violence may reduce self-esteem and ability to negotiate safer practices for fear of further violence or lead to increased drug use as a way of coping. Other evidence from the region shows that aggressive policing practices exacerbate the potential for HIV risk. This is through forcing women to work longer hours to make up time after arrest, having unprotected sex for more money to make up lost income, and not carrying condoms as they may be used as evidence of sex work. The data presented in the study provides further evidence of police involvement in sex work. It also shows that the police and protection gangs both expect free sex. Sexual violence from the police is well-established it has an official name ‘subbotnik’.  Findings confirm the need for sex worker interventions to address injecting practices and sexual health, as well as strategies to reduce violence. This is important, since historically across Russia sex worker interventions have been set up within harm reduction services with a focus on reducing injecting related harms and providing limited sexual health support. It also reiterates the need for multi-level interventions to reduce levels of violence including changes to legislation regulating sex work and community level interventions to enable women to work together.

Europe
Russian Federation
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Needle syringe programmes are effective structural interventions

Effectiveness of Structural-Level Needle/Syringe Programs to Reduce HCV and HIV Infection Among People Who Inject Drugs: A Systematic Review.

Abdul-Quader AS, Feelemyer J, Modi S, Stein ES, Briceno A, Semaan S, Horvath T, Kennedy GE, Des Jarlais DC. AIDS Behav. 2013 Aug 22. [Epub ahead of print]

Needle-syringe programs (NSP) have been effective in reducing HIV and hepatitis C (HCV) infection among people who inject drugs (PWID). Achieving sustainable reductions in these blood-borne infections requires addressing structural factors so PWID can legally access NSP services. Systematic literature searches collected information on NSP coverage and changes in HIV or HCV infection prevalence or incidence at the population level. Included studies had to document biomarkers (HIV or HCV) coupled with structural-level NSP, defined by a minimum 50% coverage of PWID and distribution of 10 or more needles/syringe per PWID per year. Fifteen studies reported structural-level NSP and changes in HIV or HCV infection prevalence/incidence. Nine reported decreases in HIV prevalence, six in HCV infection prevalence, and three reported decreases in HIV incidence. The results support NSP as a structural-level intervention to reduce population-level infection and implementation of NSP for prevention and treatment of HIV and HCV infection.

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Editor’s notes: Injection drug use is one of the most efficient modes of transmission of human immunodeficiency virus (HIV), hepatitis C (HCV), and other blood-borne diseases. There are an estimated 16 million people who inject drugs (PWID) worldwide, of whom approximately 3 million are estimated to be HIV-positive. Structural interventions focus on contextual or environmental factors that influence risk behaviour, rather than characteristics of individuals who engage in risk behaviours. This paper reviewed evidence from studies that included interventions that evaluated changes in policies, laws and regulations in relation to access and availability of sterile injecting equipment, use of public funds for establishing structural level large-scale syringe access programmes (NSP), and distribution of sterile equipment at the population level. The findings highlight the importance of establishing structural-level large-scale syringe access programmes for HIV prevention, especially early in an epidemic among PWID.  Further, it emphasizes that significant public health benefits can be obtained even when at least 50% of the injecting population in a community receive at least 10 or more sterile syringes per year.

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Sexual transmission in St Petersburg may be self-sustaining without improved surveillance and prevention among partners of people who inject drugs

HIV transmission from drug injectors to partners who do not inject, and beyond: Modelling the potential for a generalised heterosexual epidemic in St Petersburg, Russia.

Mills HL, White E, Colijn C, Vickerman P, Heimer R. Drug Alcohol Depend. 2013 May 18. [Epub ahead of print]

Background: HIV infection is prevalent among drug injectors in St. Petersburg and their non-injecting heterosexual partners (PIDUs). There are fears that sexual transmission of HIV from IDUs to PIDUs may portend a self-sustaining, heterosexual epidemic in Russia.

Methods: Our model combines a network model of sexual partnerships of IDUs and non-IDUs to represent sexual transmission of HIV and a deterministic model for parenteral transmission among IDUs. Behavioural parameters were obtained from a survey of St. Petersburg IDUs and their sexual partners. We based our model fits on two scenarios for PIDU prevalence in 2006 (5.6% and 15.1%, calculated excluding and including HCV co-infected PIDUs respectively) and compared predictions for the general population HIV prevalence.

Results: Results indicate that sexual transmission could sustain a non-IDU HIV epidemic. The model indicates that general population prevalence may be greater than current estimates imply. Parenteral transmission drives the epidemic and the PIDU bridge population plays a crucial role transferring infection to non-IDUs. The model indicates that the high PIDU prevalence is improbable because of the high risk behaviour this implies; the lower prevalence is possible.

Conclusion: The model implies that transmission through PIDUs will sustain a heterosexual epidemic, if prevalence among IDUs and PIDUs is as high as survey data suggest. We postulate that current estimates of population prevalence underestimate the extent of the HIV epidemic because they are based on the number of registered cases only. Curtailing transmission among injectors and PIDUs will be vital in controlling heterosexual transmission.

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Editor’s notes: Current estimates of HIV prevalence both in the general population and in people who inject drugs in St Petersburg may under-estimate true prevalence due to imperfect methods of collecting surveillance data.  The models in this study are based on a large respondent-driven sample of people who inject drugs, men who have sex with men, and their sexual partners.  The results indicate that HIV prevalence in the general population may be at least twice as high as is higher than the current surveillance data imply, even under conservative assumptions.  Furthermore, models that removed parenteral transmission from 2012 onwards (i.e. assuming 100% treatment strategy), the epidemic among people not injecting drugs would be sustained.  These findings highlight the importance of improving surveillance and prevention activities in the bridging population in order to control the HIV epidemic, in addition to focusing on prevention and treatment of people who inject drugs.

Europe
Russian Federation
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Declines in HIV incidence and risk behaviours among drug users in Amsterdam

Drug Users in Amsterdam: Are They Still at Risk for HIV?

Nienke van der Knaap, Bart P. X. Grady, Maarten F. Schim van der Loeff, Titia Heijman, Arjen Speksnijder, Ronald Geskus, Maria Prins. PLoS One. 2013;8(3):e59125. doi: 10.1371/journal.pone.0059125. Epub 2013 Mar 18.

Background and Aims: To examine whether drug users (DU) in the Amsterdam Cohort Study (ACS) are still at risk for HIV, we studied trends in HIV incidence and injecting and sexual risk behaviour from 1986 to 2011.

Methods: The ACS is an open, prospective cohort study on HIV. Calendar time trends in HIV incidence were modelled using Poisson regression. Trends in risk behaviour were modelled via generalized estimating equations. In 2010, a screening for STI (chlamydia, gonorrhoea and syphilis) was performed. Determinants of unprotected sex were studied using logistic regression analysis.

Results: The HIV incidence among 1298 participants of the ACS with a total follow-up of 12,921 person-years (PY) declined from 6.0/100 PY (95% confidence interval [CI] 3.2–11.1) in 1986 to less than 1/100 PY from 1997 onwards. Both injection and sexual risk behaviour declined significantly over time. Out of 197 participants screened for STI in 2010–2011, median age 49 years (IQR 43–59), only 5 (2.5%) were diagnosed with an STI. In multivariable analysis, having a steady partner (aOR 4.1, 95% CI 1.6–10.5) was associated with unprotected sex. HIV-infected participants were less likely to report unprotected sex (aOR 0.07, 95% CI 0.02–0.37).

Conclusions: HIV incidence and injection risk behaviour declined from 1986 onwards. STI prevalence is low; unprotected sex is associated with steady partners and is less common among HIV-infected participants. These findings indicate a low transmission risk of HIV and STI, which suggests that DU do not play a significant role in the current spread of HIV in Amsterdam.

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Editor’s notes: Drug users are at high risk of HIV, both from the risk of HIV arising from sharing injecting paraphernalia, along with HIV risks from sexual behaviour – including the increased risk of unprotected sex associated with the use of cocaine and other stimulants, or if drug users work as commercial sex workers. Earlier research showed a decline in injecting risk behaviour up to 2005, but a remaining risk of HIV transmission from sexual risk behaviour. This analysis shows that risk from injecting has continued to decline. The prevalence of unprotected sex was substantial, but mainly associated with having a steady partner, and was less common in HIV-infected participants. Taken together, the findings indicate a low transmission risk of HIV and STI in this population cohort, and suggest that drug use no longer plays a significant role in the spread of HIV in Amsterdam. This is in contrast to the increasing levels of HIV infection among drug users in other Eastern European settings, and underscores the importance of effective harm reduction programmes for drug users.  

Europe
Netherlands
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Good treatment outcomes in a drug-user centered national HIV treatment program

Outcomes of antiretroviral therapy in Vietnam: results from a national evaluation.

Nguyen DB, Do NT, Shiraishi RW, Le YN, Tran QH, Huu Nguyen H, Medland N, Nguyen LT, Struminger BB. PLoS One. 2013;8(2):e55750. doi: 10.1371/journal.pone.0055750. Epub 2013 Feb 15.

Vietnam has significantly scaled up its national antiretroviral therapy (ART) program since 2005. With the aim of improving Vietnam's national ART program, we conducted an outcome evaluation of the first five years of the program in this concentrated HIV epidemic where the majority of persons enrolled in HIV care and treatment services are people who inject drugs (PWID). The results of this evaluation may have relevance for other national ART programs with significant PWID populations. Retrospective cohort analysis of patients at 30 clinics randomly selected with probability proportional to size among 120 clinics with at least 50 patients on ART. Charts of patients whose ART initiation was at least 6 months prior to the study date were abstracted. Depending on clinic size, either all charts or a random sample of 300 charts were selected. Analyses were limited to treatment-naïve patients. Multiple imputations were used for missing data. Of 7,587 patient charts sampled, 6,875 were those of treatment-naïve patients (74.4% male, 95% confidence interval [CI]: 72.4-76.5, median age 30, interquartile range [IQR]: 26-34, 62.0% reported a history of intravenous drug use, CI: 58.6-65.3). Median baseline CD4 cell count was 78 cells/mm (IQR: 30-162) and 30.4% (CI: 25.8-35.1) of patients were at WHO stage IV. The majority of patients started d4T/3TC/NVP (74.3%) or d4T/3TC/EFV (18.6%). Retention rates after 6, 12, 24, and 36 months were 88.4% (CI: 86.8-89.9), 84.0% (CI: 81.8-86.0), 78.8% (CI: 75.7-81.6), and 74.6% (CI: 69.6-79.0). Median CD4 cell count gains after 6, 12, 24, and 36 months were 94 (IQR: 45-153), 142 (IQR: 78-217), 213 (IQR: 120-329), and 254 (IQR: 135-391) cells/mm. Patients who were PWID showed significantly poorer retention. The study showed good retention and immunological response to ART among a predominantly PWID group of patients despite advanced HIV infections at baseline.

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Editor’s notes: The HIV epidemic is concentrated among key populations, primarily among people who inject drugs, and less so among men who have sex with men, and sex workers. As of December 2011 an estimated 53% of those clinically or immunologically eligible. While concerns remain regarding the human rights of key populations in Vietnam, of note needle and syringe programs and methadone maintenance programs, key HIV prevention interventions, are available in most provinces. This study reviewed chart information on almost 7000 patients. 62% of patients on ART had a history of intravenous drug use and most patients started on ART at fairly advanced immunosuppression. Retention at 6 and 12 months was quite high for patients with and without a history of IV drug use- those with such a history began to have significantly lower retention by 2 years after treatment initiation. This study was not able to tease out the reasons for this later divergence in retention results.

People who use drugs remain a key population – well designed and managed programs can overcome previously raised concerns about the ability to engage and maintain drug users in HIV care. In addition to directly sensitizing the care and treatment programs to the specific needs of drugs users, syringe and needle exchange programs and provision of opioid substitution therapy have been demonstrated to have a HIV prevention impact. Given the relatively recent expansion of such services in Vietnam, hopefully more recent data will demonstrate a further narrowing of the retention differences between drug users and other populations on HIV treatment.

Asia
Viet Nam
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Harm reduction among drug users dramatically reduces new HIV and Hepatitis C virus infections

Decline in incidence of HIV and Hepatitis C virus infection among injecting drug users in Amsterdam; evidence for harm reduction?

de Vos AS, van der Helm JJ, Matser A, Prins M, Kretzschmar ME. Addiction. 2013 Jan 24. doi: 10.1111/add.12125. [Epub ahead of print]

In Amsterdam HIV prevalence has nearly halved among injecting drug users since 1990. Hepatitis C Virus (HCV) prevalence also declined, HIV and HCV incidence dropped to nearly zero. The authors examined possible explanations for these time trends, among which the implementation of harm reduction measures aimed at reducing risk behavior of IDU. Individual-based modeling of the spread of HIV and HCV was used. Information about demographic parameters was obtained from the Amsterdam Cohort Study (ACS) among drug users. The model included changes in inflow of new IDU and death-rates over time, the latter dependent on age and time since HIV-seroconversion. Different scenarios of risk behavior were considered. Simulated HIV and HCV incidence and prevalence were compared with ACS data. Assuming harm reduction measures had led to strong decrease in risk-behavior over time improved the model fit (squared residuals decreased by 30%). Substantial incidence and HIV prevalence decline were reproduced by incorporating demographic changes in the model. In particular, lowered disease spread might be a result of depletion of high-risk IDU among those at risk for disease, and a decrease in the number of high-risk individuals in the population due to HIV-related mortality. Marked decreases in HIV and HCV in Amsterdam since 1990 could be partly due to harm reduction measures; however, they may also be largely attributable to changes in the IDU population. Future research aimed at quantifying the benefits of interventions should not neglect the impact of natural epidemic progression and demographic changes.

Abstract access 

Editor’s notes: This article from Amsterdam highlights the impressive information that HIV and HCV incidence has dropped nearly to zero among drug users. Modeling exercises indicate that it is a challenge to attribute the cause of these results, however clearly harm reduction measures have been widely implemented, beyond the level seen in many other countries where drug users are a key population at risk for HIV acquisition.

Europe
Netherlands
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