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Access to treatment and medication for opioid use disorder (MOUD) is essential in reducing opioid use and associated behavioral risks, such as syringe sharing among persons who inject drugs (PWID). Syringe sharing among PWID carries high risk of transmission of serious infections such as hepatitis C and HIV. MOUD resources, such as methadone provider clinics, however, are often unavailable to PWID due to barriers like long travel distance to the nearest methadone provider and the required frequency of clinic visits. The goal of this study is to examine the uncertainty in the effects of travel distance in initiating and continuing methadone treatment and how these interact with different spatial distributions of methadone providers to impact co-injection (syringe sharing) risks. A baseline scenario of spatial access was established using the existing locations of methadone providers in a geographical area of metropolitan Chicago, Illinois, USA. Next, different counterfactual scenarios redistributed the locations of methadone providers in this geographic area according to the densities of both the general adult population and according to the PWID population per zip code. We define different reasonable methadone access assumptions as the combinations of short, medium, and long travel distance preferences combined with three urban/suburban travel distance preference. Our modeling results show that when there is a low travel distance preference for accessing methadone providers, distributing providers near areas that have the greatest need (defined by density of PWID) is best at reducing syringe sharing behaviors. However, this strategy also decreases access across suburban locales, posing even greater difficulty in regions with fewer transit options and providers. As such, without an adequate number of providers to give equitable coverage across the region, spatial distribution cannot be optimized to provide equitable access to all PWID. Our study has important implications for increasing interest in methadone as a resurgent treatment for MOUD in the United States and for guiding policy toward improving access to MOUD among PWID. Author summary: Persons who inject drugs (PWID) such as heroin or other illicit substances are at increased risk of getting or transmitting HIV or hepatitis C (HCV) infection, because limited access to clean syringes and drug injection equipment means that PWID often share contaminated syringes. Public health interventions aimed at reducing injection drug use include medications for opioid use disorder (MOUD) that help to reduce cravings for opioids like heroin and fentanyl. However, resources like MOUD provider clinics are often unavailable to PWID due to factors such as the travel distance from home to clinic, frequent clinic visits, along with social phenomena such as degree of medical mistrust and stigma towards treatment. We use a computational simulation model of PWID social networks and drug use behaviors in Chicago, IL and suburbs to show how the geographic distribution of clinical providers of methadone, an MOUD, impacts the injection frequency of PWID. Our modeling results show that when PWID prefer a low travel distance to methadone providers, distributing providers near areas that have the greatest need is best at reducing syringe sharing behaviors. However, this strategy also decreases access across suburban locales, posing even greater difficulty in regions with fewer transit options and providers. [ABSTRACT FROM AUTHOR]

Background: Sharing of syringes is the leading transmission pathway for hepatitis C (HCV) infections. The extent to which HCV can spread among people who inject drugs (PWID) is largely dependent on syringe-sharing network factors. Our study aims to better understand partnership characteristics and syringe and equipment sharing with those partners, including measures of relationship closeness, sexual activity, and social support, as well as self and partner HCV status to better inform interventions for young urban and suburban PWID. Methods: Data are from baseline interviews of a longitudinal network-based study of young (aged 18–30) PWID (egos) and their injection network members (alters) in metropolitan Chicago (n = 276). All participants completed a computer-assisted interviewer-administered questionnaire and an egocentric network survey on injection, sexual, and support networks. Results: Correlates of syringe and ancillary equipment sharing were found to be similar. Sharing was more likely to occur in mixed-gender dyads. Participants were more likely to share syringes and equipment with injection partners who lived in the same household, who they saw every day, who they trusted, who they had an intimate relationship with that included condomless sex, and who provided personal support. PWID who had tested HCV negative within the past year were less likely to share syringes with an HCV positive partner compared to those who did not know their status. Conclusion: PWID regulate their syringe and other injection equipment sharing to some extent by sharing preferentially with injection partners with whom they have a close personal or intimate relationship, and whose HCV status they are more likely to know. Our findings underscore the need for risk interventions and HCV treatment strategies to consider the social context of syringe and equipment sharing within partnerships. [ABSTRACT FROM AUTHOR]

Background: Hepatitis C (HCV) infection has been rising in the suburban and rural USA, mainly via injection-based transmission. Injection and sexual networks are recognized as an important element in fostering and preventing risky behavior; however, the role of social support networks has received somewhat less attention. Methods: Using baseline data from an ongoing longitudinal study, we examined the composition and structure of injection drug use (IDU), sex, and social support networks of young people who inject drugs (aged 18–30) and their injection network members. Lasso logistic regression was used to select a subset of network characteristics that were potentially important predictors of injection risk behaviors and HCV exposure. Results: Several measures of IDU, sexual, and support network structure and composition were found to be associated with HCV exposure, receptive syringe sharing (RSS), and ancillary equipment sharing. Gender and sexual relationships were important factors for all risk behaviors. Support network characteristics were also important, notably including a protective effect of majority Hispanic support networks for RSS and HCV exposure. Both IDU network residence heterogeneity and support network geography were associated with injection equipment sharing. Conclusions: The associations of IDU and support network geography with equipment sharing highlight the need to extend harm reduction efforts beyond urban areas. Greater understanding of support network influences on risk behavior may provide important insights to strengthen the benefits of harm reduction. In considering the probability of HCV transmission, it is important to consider setting and network structures that promote propagation of risk. [ABSTRACT FROM AUTHOR]

Hepatitis C virus (HCV) infection is a leading cause of chronic liver disease and mortality worldwide. Direct-acting antiviral (DAA) therapy leads to high cure rates. However, persons who inject drugs (PWID) are at risk for reinfection after cure and may require multiple DAA treatments to reach the World Health Organization's (WHO) goal of HCV elimination by 2030. Using an agent-based model (ABM) that accounts for the complex interplay of demographic factors, risk behaviors, social networks, and geographic location for HCV transmission among PWID, we examined the combination(s) of DAA enrollment (2.5%, 5%, 7.5%, 10%), adherence (60%, 70%, 80%, 90%) and frequency of DAA treatment courses needed to achieve the WHO's goal of reducing incident chronic infections by 90% by 2030 among a large population of PWID from Chicago, IL and surrounding suburbs. We also estimated the economic DAA costs associated with each scenario. Our results indicate that a DAA treatment rate of >7.5% per year with 90% adherence results in 75% of enrolled PWID requiring only a single DAA course; however 19% would require 2 courses, 5%, 3 courses and <2%, 4 courses, with an overall DAA cost of $325 million to achieve the WHO goal in metropolitan Chicago. We estimate a 28% increase in the overall DAA cost under low adherence (70%) compared to high adherence (90%). Our modeling results have important public health implications for HCV elimination among U.S. PWID. Using a range of feasible treatment enrollment and adherence rates, we report robust findings supporting the need to address re-exposure and reinfection among PWID to reduce HCV incidence. [ABSTRACT FROM AUTHOR]

Progress toward hepatitis C virus (HCV) elimination in the United States is not on track to meet targets set by the World Health Organization, as the opioid crisis continues to drive both injection drug use and increasing HCV incidence. A pragmatic approach to achieving this is using a microelimination approach of focusing on high-risk populations such as people who inject drugs (PWID). Computational models are useful in understanding the complex interplay of individual, social, and structural level factors that might alter HCV incidence, prevalence, transmission, and treatment uptake to achieve HCV microelimination. However, these models need to be informed with realistic sociodemographic, risk behavior and network estimates on PWID. We conducted a meta-analysis of research studies spanning 20 years of research and interventions with PWID in metropolitan Chicago to produce parameters for a synthetic population for realistic computational models (e.g., agent-based models). We then fit an exponential random graph model (ERGM) using the network estimates from the meta-analysis in order to develop the network component of the synthetic population. [ABSTRACT FROM AUTHOR]

Background/Aim: New direct-acting antivirals (DAAs) provide an opportunity to combat hepatitis C virus (HCV) infection in persons who inject drugs (PWID). Here we use a mathematical model to predict the impact of a DAA-treatment scale-up on HCV prevalence among PWID and the estimated cost in metropolitan Chicago. Methods: To estimate the HCV antibody and HCV-RNA (chronic infection) prevalence among the metropolitan Chicago PWID population, we used empirical data from three large epidemiological studies. Cost of DAAs is assumed $50,000 per person. Results: Approximately 32,000 PWID reside in metropolitan Chicago with an estimated HCV-RNA prevalence of 47% or 15,040 cases. Approximately 22,000 PWID (69% of the total PWID population) attend harm reduction (HR) programs, such as syringe exchange programs, and have an estimated HCV-RNA prevalence of 30%. There are about 11,000 young PWID (<30 years old) with an estimated HCV-RNA prevalence of 10% (PWID in these two subpopulations overlap). The model suggests that the following treatment scale-up is needed to reduce the baseline HCV-RNA prevalence by one-half over 10 years of treatment [cost per year, min-max in millions]: 35 per 1,000 [$50-$77] in the overall PWID population, 19 per 1,000 [$20-$26] for persons in HR programs, and 5 per 1,000 [$3-$4] for young PWID. Conclusions: Treatment scale-up could dramatically reduce the prevalence of chronic HCV infection among PWID in Chicago, who are the main reservoir for on-going HCV transmission. Focusing treatment on PWID attending HR programs and/or young PWID could have a significant impact on HCV prevalence in these subpopulations at an attainable cost. [ABSTRACT FROM AUTHOR]

Highlights • Persons who inject drugs (PWID) are at risk for transmitting Hepatitis C virus (HCV) infection. • Though direct-acting antiviral (DAA) therapy cures >90%, it does not prevent reinfection. • Development of an HCV vaccine represents a critical intervention to prevent HCV re/infection. • Modeling suggests that augmenting DAA with vaccines would rapidly decline new HCV re/infections. Abstract Background and aims Persons who inject drugs (PWID) are at highest risk for acquiring and transmitting hepatitis C (HCV) infection. The recent availability of oral direct-acting antiviral (DAA) therapy with reported cure rates >90% can prevent HCV transmission, making HCV elimination an attainable goal among PWID. The World Health Organization (WHO) recently proposed a 90% reduction in HCV incidence as a key objective. However, given barriers to the use of DAAs in PWID, including cost, restricted access to DAAs, and risk of reinfection, combination strategies including the availability of effective vaccines are needed to eradicate HCV as a public health threat. This study aims to model the cost and efficacy of a dual modality approach using HCV vaccines combined with DAAs to reduce HCV incidence by 90% and prevalence by 50% in PWID populations. Methods We developed a mathematical model that represents the HCV epidemic among PWID and calibrated it to empirical data from metropolitan Chicago, Illinois. Four medical interventions were considered: vaccination of HCV naive PWID, DAA treatment, DAA treatment followed by vaccination, and, a combination of vaccination and DAA treatment. Results The combination of vaccination and DAAs is the lowest cost-expensive intervention for achieving the WHO target of 90% incidence reduction. The use of DAAs without a vaccine is much less cost-effective with the additional risk of reinfection after treatment. Vaccination of naïve PWID alone, even when scaled-up to all reachable PWID, cannot achieve 90% reduction of incidence in high-prevalence populations due to infections occurring before vaccination. Similarly, the lowest cost-expensive way to halve prevalence in 15 years is through the combination of vaccination and DAAs. Conclusions The modeling results underscore the importance of developing an effective HCV vaccine and augmenting DAAs with vaccines in HCV intervention strategies in order to achieve efficient reductions in incidence and prevalence. [ABSTRACT FROM AUTHOR]

Background: Among young people who inject drugs (PWID) homelessness is associated with numerous adverse psychosocial and health consequences, including risk of relapse and overdose, psychological distress and suicidality, limited treatment access, and injection practices that increase the risk of HIV and hepatitis C (HCV) transmission. Homeless PWID may also be less likely to access sterile syringes through pharmacies or syringe service programs.Methods: This study applied random-effects meta-regression to examine trends over time in injection risk behaviors and homelessness among young PWID in Chicago and surrounding suburban and rural areas using data from 11 studies collected between 1997 and 2017. In addition, subject-level data were pooled to evaluate the effect of homelessness on risk behaviors across all studies using mixed effects logistic and negative binomial regression with random study effects.Results: There was a significant increase in homelessness among young PWID over time, consistent with the general population trend of increasing youth homelessness. In mixed-effects regression, homelessness was associated with injection risk behaviors (receptive syringe sharing, syringe mediated sharing, equipment sharing) and exchange sex, though we detected no overall changes in risk behavior over time.Conclusions: Increases over time in homelessness among young PWID highlight a need for research to understand factors contributing to youth homelessness to inform HIV/STI, HCV, and overdose prevention and intervention services for this population. [ABSTRACT FROM AUTHOR]

Opioid use has been increasing at alarming rates over the past 15 years, yet uptake of medication for opioid use disorder (MOUD) remains low. Much of the research on individual characteristics predicting MOUD uptake is equivocal, and there is a dearth of research on setting-level and network-level characteristics that predict MOUD uptake. Towards a more holistic, multilevel understanding, we explore individual-level, network-level, and community-level characteristics associated with MOUD uptake. Baseline data from a longitudinal study of young people who inject drugs and their injection and support network members living in Chicago (N = 165) was used to conduct cross-sectional multilevel logistic regression analyses to examine associations between MOUD uptake and a set of potential predictors at the individual-, network-, and community-levels that were chosen based on theoretical relevance or support from previous empirical studies. Stigma at both the individual and community levels was significantly associated with MOUD uptake (though in different directions). Greater individual-level stigma was associated with a higher likelihood of MOUD uptake, while having a more normatively stigmatizing community environment was associated with a lower likelihood of MOUD uptake. Using heroin and cocaine simultaneously and having a larger support network were associated with a greater likelihood of MOUD uptake. The present study's holistic, multilevel approach identified three individual-level characteristics, one network-level characteristic, and one community-level characteristic associated with MOUD uptake. However, more research is needed examining multilevel predictors, to help with developing interventions addressing barriers to MOUD use at multiple levels of influence. • Individual, network, and community characteristics were associated with MOUD uptake. • Individual & community-level stigma had different patterns of association with MOUD. • Concurrent substance use and support network size significantly predicted MOUD uptake. • A multilevel approach is important to understanding predictors of MOUD uptake. [ABSTRACT FROM AUTHOR]

Background: Identifying risk for hepatitis C (HCV) infection is important for understanding recent increases in HCV incidence among young people who inject drugs (PWID) in suburban and rural areas; and for refining the targeting of effective HCV preventive interventions. Much of the extant research has focused on individual health behaviors (e.g., risky drug injection behaviors) as predictors of HCV infection. The present study examines two social factors (substance use-related stigma and injection-related social norms), and the interaction between these factors, as predictors of HCV infection.Methods: Baseline data were used from an ongoing longitudinal study of young PWID (N = 279; mean age = 30.4 years) from the Chicago suburbs and their injection risk network members. Adjusted logistic regression models were used to examine relationships among substance use-related stigma, safer injection norms, and HCV infection.Results: Despite a marginal bivariate association between less safe injection norms and HCV infection (OR = 0.74; 95 % CI[0.39, 1.02]; p = .071), a significant stigma X norms interaction (AOR = 0.68; 95 % CI[0.51, 0.90]) suggested that at high levels of stigma, probability of HCV infection was high regardless of injection norms.Conclusions: Findings suggest that social factors - specifically, substance use-related stigma and injection norms - are important predictors of HCV infection risk. The interaction found between these social factors suggests that intervening only to change injection norms or behaviors is likely insufficient to reduce risk for HCV infection in high-stigma settings or among high-stigma populations. Future research should develop and evaluate stigma-reduction interventions in combination with safer-injection interventions in order to maximize HCV risk reduction. [ABSTRACT FROM AUTHOR]