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Latinx people who inject drugs (PWID) are less likely to engage in injection equipment sharing, but are more vulnerable to injection drug use (IDU)-related morbidity and mortality than Whites. Identifying subgroups of Latinx PWID who do engage in equipment sharing and likely bear the brunt of this health burden is a priority. Ethnic disparities may reflect contextual drivers, including injection networks. Latinx PWID with low ethnic homophily (the proportion of individuals with the same ethnic background) may be more likely to share equipment due to forced distancing from health-protective ethnocultural resources and power imbalances within injection networks. The current study offers a framework and examines how associations between network ethnic homophily and injection equipment sharing differ among 74 Latinx and 170 non-Latinx White PWID in the Chicagoland area ( N  = 244). Latinx had less homophilous than non-Latinx Whites ( p <.001). Ethnic homophily was protective for equipment sharing among Latinx ( OR  = 0.17, 95%CI [0.77, 0.04], p = .02), but not non-Latinx Whites ( OR  = 1.66, 95%CI [0.40, 6.93], p = .49). Our findings implicate the need for targeted cultured interventions that focus on Latinx PWID who are more vulnerable to morbidity and mortality, potentially due to less access to ethnic peers.

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., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Tatara et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Despite the availability of direct-acting antivirals that cure individuals infected with the hepatitis C virus (HCV), developing a vaccine is critically needed in achieving HCV elimination. HCV vaccine trials have been performed in populations with high incidence of new HCV infection such as people who inject drugs (PWID). Developing strategies of optimal recruitment of PWID for HCV vaccine trials could reduce sample size, follow-up costs and disparities in enrollment. We investigate trial recruitment informed by machine learning and evaluate a strategy for HCV vaccine trials termed PREDICTEE-Predictive Recruitment and Enrichment method balancing Demographics and Incidence for Clinical Trial Equity and Efficiency. PREDICTEE utilizes a survival analysis model applied to trial candidates, considering their demographic and injection characteristics to predict the candidate's probability of HCV infection during the trial. The decision to recruit considers both the candidate's predicted incidence and demographic characteristics such as age, sex, and race. We evaluated PREDICTEE using in silico methods, in which we first generated a synthetic candidate pool and their respective HCV infection events using HepCEP, a validated agent-based simulation model of HCV transmission among PWID in metropolitan Chicago. We then compared PREDICTEE to conventional recruitment of high-risk PWID who share drugs or injection equipment in terms of sample size and recruitment equity, with the latter measured by participation-to-prevalence ratio (PPR) across age, sex, and race. Comparing conventional recruitment to PREDICTEE found a reduction in sample size from 802 (95%: 642-1010) to 278 (95%: 264-294) with PREDICTEE, while also reducing screening requirements by 30%. Simultaneously, PPR increased from 0.475 (95%: 0.356-0.568) to 0.754 (95%: 0.685-0.834). Even when targeting a dissimilar maximally balanced population in which achieving recruitment equity would be more difficult, PREDICTEE is able to reduce sample size from 802 (95%: 642-1010) to 304 (95%: 288-322) while improving PPR to 0.807 (95%: 0.792-0.821). PREDICTEE presents a promising strategy for HCV clinical trial recruitment, achieving sample size reduction while improving recruitment equity.

Background: Recent studies underscore the significance of adopting a syndemics approach to study opioid misuse, overdose, hepatitis C (HCV) and HIV infections, within the broader context of social and environmental contexts in already marginalized communities. Social interactions and spatial contexts are crucial structural factors that remain relatively underexplored. This study examines the intersections of social interactions and spatial contexts around injection drug use. More specifically, we investigate the experiences of different residential groups among young (aged 18-30) people who inject drugs (PWID) regarding their social interactions, travel behaviors, and locations connected to their risk behaviors. By doing so, we aim to achieve a more comprehensive understanding of the multidimensional risk environment, thereby facilitating the development of informed policies., Methods: We collected and examined data regarding young PWID's egocentric injection network and geographic activity spaces (i.e., where they reside, inject drugs, purchase drugs, and meet sex partners). Participants were stratified based on the location of all place(s) of residence in the past year i.e., urban, suburban, and transient (both urban and suburban) to i) elucidate geospatial concentration of risk activities within multidimensional risk environments based on kernel density estimates; and ii) examine spatialized social networks for each residential group., Results: Participants were mostly non-Hispanic white (59%); 42% were urban residents, 28% suburban, and 30% transient. We identified a spatial area with concentrated risky activities for each residential group on the West side of Chicago in Illinois where a large outdoor drug market area is located. The urban group (80%) reported a smaller concentrated area (14 census tracts) compared to the transient (93%) and suburban (91%) with 30 and 51 tracts, respectively. Compared to other areas in Chicago, the identified area had significantly higher neighborhood disadvantages. Significant differences were observed in social network structures and travel behaviors: suburban participants had the most homogenous network in terms of age and residence, transient participants had the largest network (degree) and more non-redundant connections, while the urban group had the shortest travel distance for all types of risk activities., Conclusion: Distinct residential groups exhibit varying patterns of network interaction, travel behaviors, and geographical contexts related to their risk behaviors. Nonetheless, these groups share common concentrated risk activity spaces in a large outdoor urban drug market area, underscoring the significance of accounting for risk spaces and social networks in addressing syndemics within PWID populations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

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., (© 2023. The Author(s).)

Background: 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., Methods: 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., Results: 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., Conclusions: 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., Competing Interests: Conflict of interest None of the authors have any conflicts to report., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: In many countries with high levels of COVID-19 vaccine access, uptake remains a major issue. We examined prospective predictors of COVID-19 vaccine uptake in a United States longitudinal study., Methods: An online longitudinal study on COVID-19 and well-being assessed vaccine hesitancy attitudes, social norms, and uptake among 444 respondents who had completed both survey waves in March and June 2021., Results: The mean sample age was 41, with 55% female, 71% white, 13% Black, and 6% Latinx. In March 2021, 14% had received at least one COVID-19 vaccine dose. By June 2021, 64% reported receiving at least one dose. In prospectively assessing predictors of vaccine uptake, we found strong correlations among five different vaccine hesitancy questions. In multivariable logistic regression models, family and friends discouraging vaccination (adjusted odds ratios [aOR] = .26, 95% CI = .07, .98), not knowing whom to believe about vaccine safety (aOR = .51, 95% CI = .27, .95), and concerns that shortcuts were taken with vaccine development (aOR = .43, 95% CI = .23, .81) were all independent predictors of lower vaccine uptake. Political conservatism, gender, education, and income were also independent predictors of reduced uptake. Vaccine hesitancy items were also modeled as a scale, and the scale was found to be strongly predictive of vaccine uptake., Conclusions: The findings highlight the importance of social norm interventions and suggest general and specific vaccine hesitancy attitudes, especially trust, should be considered in developing vaccine uptake programs.

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., (© 2022. The Author(s).)

People who inject drugs (PWID) are a population that disproportionately struggles with economic and mental health challenges. However, despite numerous reports of people globally experiencing new or exacerbated economic and/or mental health challenges during the COVID-19 pandemic, the literature on the effect of the pandemic on PWID and their risk for harm (e.g., overdose) remains sparse. The present study will describe reported changes during the pandemic in risk factors for drug overdose (including changes in mental health symptoms and care access) among PWID in Chicago, and it will examine associations between such risk factor changes and the experience of economic challenges during the pandemic. Participants from an ongoing longitudinal study of young PWID from the Chicago suburbs and their injection risk network members (N = 138; mean age = 28.7 years) were interviewed about changes in their experiences, substance use behavior, and mental health since the start of the COVID-19 pandemic. Bivariate cross tabulations were computed of each "overdose risk factor" with experiences of economic challenges during the pandemic. Fisher's Exact Tests were used to assess statistical significance. Adjusted logistic regression models were also conducted that controlled for sociodemographic characteristics, for time elapsed since the start of the pandemic, and for pre-pandemic income, homelessness, and injection frequency. Over half of our sample reported using alone more than usual during the pandemic, and over 40% reported using more than usual and/or buying drugs that were of a decreased purity or quality. Additionally, a large proportion of our sample (52.5% of those asked) reported more difficulty than usual accessing mental health care. Experiencing loss of a source of income during the pandemic was associated with using more drugs, using alone more, using a larger amount of drugs while using alone, wanting to stop using but being unable, and difficulty accessing mental health care. The preliminary associations found by the present study suggest that economic challenges or disruptions experienced during the pandemic are likely to increase risk for overdose among PWID experiencing such challenges, via changes in the above behaviors and/or conditions that are associated with risk for overdose. Intervention efforts should therefore be focused not only directly on overdose prevention, but also on assisting PWID with their economic challenges and helping them regain economic stability and access to services that may have been impeded by financial difficulty.

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., Competing Interests: Nothing to disclose

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., Competing Interests: The authors have declared that no competing interests exist.

Individuals with a history of opioid use are disproportionately represented in Illinois jails and prisons and face high risks of overdose and relapse at community reentry. Case management and peer recovery coaching are established interventions that may be leveraged to improve linkage to substance use treatment and supportive services during these critical periods of transition. We present the protocol for the Reducing Opioid Mortality in Illinois (ROMI), a type I hybrid effectiveness-implementation randomized trial of a case management, peer recovery coaching and overdose education and naloxone distribution (CM/PRC + OEND) critical time intervention (CTI) compared to OEND alone. The CM/PRC + OEND is a novel, 12-month intervention that involves linkage to substance use treatment and support for continuity of care, skills building, and navigation and engagement of social services that will be implemented using a hub-and-spoke model of training and supervision across the study sites. At least 1000 individuals released from jails and prisons spanning urban and rural settings will be enrolled. The primary outcome is engagement in medication for opioid use disorder. Secondary outcomes include health insurance enrollment, mental health service engagement, and re-arrest/recidivism, parole violation, and/or reincarceration. Mixed methods will be used to evaluate process and implementation outcomes including fidelity to, barriers to, facilitators of, and cost of the intervention. Videoconferencing and other remote processes will be leveraged to modify the protocol for safety during the COVID-19 pandemic. Results of the study may improve outcomes for vulnerable persons at the margin of behavioral health and the criminal legal system., (Copyright © 2021 Elsevier Inc. All rights reserved.)

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., (Copyright © 2021. Published by Elsevier B.V.)

Criminal justice involved (CJI) individuals with a history of opioid use disorder (OUD) are at high risk of overdose and death in the weeks following release from jail. We developed the Justice-Community Circulation Model (JCCM) to investigate OUD/CJI dynamics post-release and the effects of interventions on overdose deaths. The JCCM uses a synthetic agent-based model population of approximately 150,000 unique individuals that is generated using demographic information collected from multiple Chicago-area studies and data sets. We use a high-performance computing (HPC) workflow to implement a sequential approximate Bayesian computation algorithm for calibrating the JCCM. The calibration results in the simulated joint posterior distribution of the JCCM input parameters. The calibrated model is used to investigate the effects of a naloxone intervention for a mass jail release. The simulation results show the degree to which a targeted intervention focusing on recently released jail inmates can help reduce the risk of death from opioid overdose.

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., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Receptive syringe sharing (RSS) among people who inject drugs (PWID) is a risk factor for hepatitis C virus and HIV infections. PWID with borderline personality disorder (BPD) have increased risk of RSS, but it remains unclear what drives this association. This study used ecological momentary assessment (EMA) to study characteristics associated with BPD, and RSS among PWID. We recruited PWID, ages 18-35, through two Community Outreach Intervention Projects syringe service program sites in Chicago, Illinois. After a baseline interview, participants used a mobile phone app to respond to momentary surveys on mood, substance use, and injection risk behavior for two weeks. For each momentary assessment, ratings on negative mood descriptors were combined to create measures of total negative affect (NA), and NA components of dejection, shame, anger, irritability, and worry. RSS was defined by participant responses indicating that they had used a syringe that someone else had used. We estimated mixed effects logistic models, regressing RSS on baseline affect-related impulsivity, lagged momentary NA, and the interaction term. Out of 163 participants who completed at least two EMA assessments, 152 (93%) reported at least one injection event and had valid pre-injection mood assessments required to be included in the analysis. We found that affect-related impulsivity, combined with worried mood in the hours preceding the injection episode, predicted increased risk of RSS. PWID having difficulties with emotion regulation may be at increased risk of RSS during periods of anxiety or tension. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

We conducted a longitidinal assessment of 806 respondents in March, 2020 in the US to examine the trustworthiness of sources of information about COVID-19. Respondents were recontacted after four months. Information sources included mainstream media, state health departments, the CDC, the White House, and a well-known university. We also examined how demographics, political partisanship, and skepticism about COVID-19 were associated with the perceived trustworthiness of information sources and decreased trustworthiness over time. At baseline, the majority of respondants reported high trust in COVID-19 information from state health departments (75.6%), the CDC (80.9%), and a university (Johns Hopkins, 81.1%). Mainstream media was trusted by less than half the respondents (41.2%), and the White House was the least trusted source (30.9%). At the 4-month follow-up, a significant decrease in trustworthiness in all five sources of COVID-19 information was observed. The most pronounced reductions were from the CDC and the White House. In multivariate analyses, factors associated with rating the CDC, state health department, and a university as trustworthy sources of COVID-19 information were political party affiliation, level of education, and skepticism about COVID-19. The most consistent predictor of decreased trust was political party affiliation, with Democrats as compared to Republicans less likely to report decreased trust across all sources.

An estimated 4.1 million people in the United States are infected with hepatitis C virus (HCV). In 2014, the Hepatitis C Community Alliance to Test and Treat (HepCCATT) collaborative was formed to address hepatitis C in Chicago. From 2014 to 2017, the HepCCATT Case Management Program case managed 181 HCV-infected people and performed on-site capacity building at a 6-site community health center (CHC) that produced codified protocols, which were translated into a telehealth program to build capacity within CHCs to deliver hepatitis C care. HepCCATT's innovative approach to addressing multilevel barriers is a potential model for increasing access to hepatitis C care and treatment.

Hepatitis C (HCV) is a leading cause of chronic liver disease and mortality worldwide and persons who inject drugs (PWID) are at the highest risk for acquiring and transmitting HCV infection. We developed an agent-based model (ABM) to identify and optimize direct-acting antiviral (DAA) therapy scale-up and treatment strategies for achieving the World Health Organization (WHO) goals of HCV elimination by the year 2030. While DAA is highly efficacious, it is also expensive, and therefore intervention strategies should balance the goals of elimination and the cost of the intervention. Here we present and compare two methods for finding PWID treatment enrollment strategies by conducting a standard model parameter sweep and compare the results to an evolutionary multi-objective optimization algorithm. The evolutionary approach provides a pareto-optimal set of solutions that minimizes treatment costs and incidence rates.

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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Monitoring the effects of HIV prevention efforts among persons who inject drugs is key to informing prevention programs and policy., Methods: Data for this study came from the 2012 National HIV Behavioral Surveillance interviews with persons who inject drugs across 20 US cities. The present analyses include those who identified as female, ever had sex with a man, and were at risk of HIV infection (did not report a previous positive HIV test result) (n = 2624). We conducted latent class analysis to identify sexual risk classes, and modeled associations with engagement in HIV prevention services and HIV test results., Results: We identified 6 classes of sexual risk behavior: (1) low risk, (2) monogamous, (3) casual partner, (4) multiple partners, (5) exchange sex, and (6) exchange plus main partner. The class distribution was similar across the mainland regions. Bisexual orientation and homelessness were significant predictors of higher-risk class. HIV prevalence and participation in behavioral interventions did not vary significantly by risk class, while obtaining and using free condoms did. Independent of risk class, women in cities in the South were significantly less likely to use free condoms, and HIV prevalence was higher among non-Hispanic black women and women aged 40-49 years., Conclusions: Bisexual orientation and homelessness were predictors of higher risk. Condom distribution programs reached fewer women in cities in the South. Race and age disparities in HIV-positive rates persisted after adjusting for sexual risk class.

The major route of hepatitis C virus (HCV) transmission in the United States is injection drug use. We hypothesized that if an HCV vaccine were available, vaccination could affect HCV transmission among people who inject drugs by reducing HCV titers after viral exposure without necessarily achieving sterilizing immunity. To investigate this possibility, we developed a mathematical model to determine transmission probabilities relative to the HCV RNA titers of needle/syringe-sharing donors. We simulated sharing of two types of syringes fitted with needles that retain either large or small amounts of fluid after expulsion. Using previously published viral kinetics data from both naïve subjects infected with HCV and reinfected individuals who had previously cleared an HCV infection, we estimated transmission risk between pairs of serodiscordant injecting drug users, accounting for syringe type, rinsing, and sharing frequency. We calculated that the risk of HCV transmission through syringe sharing increased ~10-fold as viral titers (log 10 IU/ml) increased ~25-fold. Cumulative analyses showed that, assuming sharing episodes every 7 days, the mean transmission risk over the first 6 months was >90% between two people sharing syringes when one had an HCV RNA titer >5 log 10 IU/ml. For those with preexisting immunity that rapidly controlled HCV, the cumulative risk decreased to 1 to 25% depending on HCV titer and syringe type. Our modeling approach demonstrates that, even with transient viral replication after exposure during injection drug use, HCV transmission among people sharing syringes could be reduced through vaccination if an HCV vaccine were available., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Aims: To test the acceptability and feasibility of ecological momentary assessment (EMA) of mood and injection risk behavior among young people who inject drugs (PWID), using mobile phones., Methods: Participants were 185 PWID age 18-35 recruited from two sites of a large syringe service program in Chicago. After completing a baseline interview, participants used a mobile phone app to respond to momentary surveys on mood, substance use, and injection risk behavior for 15 days. Participants were assigned to receive surveys 4, 5, or 6 times per day., Results: Participants were 68% male, 61% non-Hispanic white, 24% Hispanic, and 5% non-Hispanic Black. Out of 185 participants, 8% (n = 15) failed to complete any EMA assessments. Among 170 EMA responders, the mean number of days reporting was 10 (SD 4.7), the mean proportion of assessments completed was 0.43 (SD 0.27), and 76% (n = 130) completed the follow-up interview. In analyses adjusted for age and race/ethnicity, women were more responsive than men to the EMA surveys in days reporting (IRR = 1.33, 95% CI 1.13-1.56), and total number of surveys completed (IRR = 1.51, 95% CI 1.18-1.93). Homeless participants responded on fewer days (IRR = 0.76, 95% CI 0.64-0.90) and completed fewer surveys (IRR = 0.70, 95% CI 0.54-0.91), and were less likely to return for follow-up (p = 0.016). EMA responsiveness was not significantly affected by the number of assigned daily assessments., Conclusions: This study demonstrated high acceptability and feasibility of EMA among young PWID, with up to 6 survey prompts per day. However, homelessness significantly hampered successful participation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Young people in the USA who inject drugs, particularly those at a risk of residence instability, experience the highest incidence of hepatitis C (HCV) infections. This study examined associations between geographic mobility patterns and sociodemographic, behavioral, and social network characteristics of 164 young (ages 18-30) persons who inject drugs (PWID). We identified a potential bridge sub-population who reported residence in both urban and suburban areas in the past year (crossover transients) and higher-risk behaviors (receptive syringe sharing, multiple sex partners) compared to their residentially localized counterparts. Because they link suburban and urban networks, crossover transients may facilitate transmission of HIV and HCV between higher and lower prevalence areas. Interventions should address risk associated with residential instability, particularly among PWID who travel between urban and suburban areas.

Background: Monitoring the effects of HIV prevention efforts on risk behaviors among persons who inject drugs is a key to inform prevention programs and policy., Methods: Using data from the 2012 National HIV Behavioral Surveillance interviews with persons who inject drugs across 20 US cities (n = 10,171), we conducted latent class analysis to identify injection risk classes and assess the relationship between engagement in prevention services and injection-related risk behavior. We conducted stratified analyses to examine the consistency of these associations across different geographical regions., Results: The latent class analysis identified 6 distinct classes of injection-related risk behavior. The class structure was consistent across regions of the United States, but the distribution of risk classes varied significantly across regions. With covariate adjustment, the South had the most high-risk behavior (21%) and the Midwest had the least (6%). Participation in syringe access services and other prevention services was the lowest in the South. Syringe access was associated with a significantly lower likelihood of membership in the highest risk class in all regions except the Midwest. Participation in individual or group intervention with a practical skills component was associated with less risky injection behavior in all regions except the Northeast. Interventions that featured only safer injection information and discussion had no relationship with risk class., Conclusions: Our findings support evidence of the effectiveness of syringe service programs and safer injection skills training in reducing high-risk injection behavior and underscore the need to improve access to these prevention interventions in the South of the United States.

Persons who inject drugs (PWID) may be at risk of acquiring HIV and sexually transmitted infections (STIs) from risky sexual practices and elevated disease prevalence within their drug injection and sexual networks. We conducted a personal (egocentric) network study of young PWID (aged 18-30) from the Chicago metropolitan area. Logistic regression with generalized estimating equations evaluated associations between individual and network factors and sexual behaviors. Of 162 participants, 116 (71.6 %) were non-Hispanic White and 135 reported on 314 sexual network members. Multiplexity-having network members with overlapping roles as injection and sexual partners-was associated with more condomless vaginal sex (aOR 5.55; 95 % CI 1.62-19.0) and anal sex (aOR 6.79; 95 % CI 2.49-18.5) and less exchange sex among women (aOR 0.12; 95 % CI 0.03-0.40), adjusting for sociodemographic and sexual network characteristics. The contribution of individual and sexual network factors to HIV/STI transmission among young PWID warrants further research.

People who inject drugs (PWID) are at high risk for blood-borne pathogens transmitted during the sharing of contaminated injection equipment, particularly hepatitis C virus (HCV). HCV prevalence is influenced by a complex interplay of drug-use behaviors, social networks, and geography, as well as the availability of interventions, such as needle exchange programs. To adequately address this complexity in HCV epidemic forecasting, we have developed a computational model, the Agent-based Pathogen Kinetics model (APK). APK simulates the PWID population in metropolitan Chicago, including the social interactions that result in HCV infection. We used multiple empirical data sources on Chicago PWID to build a spatial distribution of an in silico PWID population and modeled networks among the PWID by considering the geography of the city and its suburbs. APK was validated against 2012 empirical data (the latest available) and shown to agree with network and epidemiological surveys to within 1%. For the period 2010-2020, APK forecasts a decline in HCV prevalence of 0.8% per year from 44(± 2)% to 36(± 5)%, although some sub-populations would continue to have relatively high prevalence, including Non-Hispanic Blacks, 48(± 5)%. The rate of decline will be lowest in Non-Hispanic Whites and we find, in a reversal of historical trends, that incidence among non-Hispanic Whites would exceed incidence among Non-Hispanic Blacks (0.66 per 100 per years vs 0.17 per 100 person years). APK also forecasts an increase in PWID mean age from 35(± 1) to 40(± 2) with a corresponding increase from 59(± 2)% to 80(± 6)% in the proportion of the population >30 years old. Our studies highlight the importance of analyzing subpopulations in disease predictions, the utility of computer simulation for analyzing demographic and health trends among PWID and serve as a tool for guiding intervention and prevention strategies in Chicago, and other major cities.

Background: Little is known about young persons who inject drugs (PWID), who are increasingly from suburban communities and predominantly non-Hispanic white., Methods: We conducted a cross-sectional personal network (egocentric) and geographic study of young PWID and their drug-using, sexual, and support network members in 2012-13 in metropolitan Chicago, Illinois, U.S., Results: We enrolled 164 young (median age=26), mostly male (65%), non-Hispanic white PWID (71%), with a self-reported HCV prevalence of 13%. Many (59%) reported multiple residences (i.e., were transient) in the past year, 45% of whom reported living in both urban and suburban places (i.e., were cross-over transients). In multivariable analyses that adjusted for participant and network member characteristics, (1) large injection networks were more common among homeless participants; and (2) syringe sharing was (a) highest among cross-over transients compared to suburban (OR=4.19 95% CI 1.69-10.35) and urban only residents (OR=2.91 95% CI 1.06-8.03), (b) higher among HCV-unknown compared HCV-negative participants (OR=4.62 95% CI 1.69-10.35), (c) more likely with network members who were cross-over transients compared to urban (OR=4.94, 95% CI 2.17-11.23) and (d) less likely with network members with HCV-unknown compared to HCV-negative status (OR=0.4 95% CI 0.19-0.84)., Conclusions: We identified homelessness as a significant risk factor for large networks and cross-over transience as a significant risk factor for syringe sharing. Further research is needed to understand the role of geographic factors promoting higher risk among these crossover transient PWID., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

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.

The aim of this study was to investigate the effects of transitioning from non-injection heroin use to injection drug use on sexual risk behavior. Non-injecting heroin users age 16-30 were enrolled from 2002 to 2005, and were re-interviewed at 6-month intervals for up to three years; 561 participants completed at least one follow-up interview. The majority of participants were non-Hispanic (NH) Black (54 %), 23 % were Hispanic, and 21 % were NH white. During follow-up, 154 participants (27.5 %) transitioned to injecting drugs. Logistic regression analyses were conducted using generalized estimating equations (GEE) to estimate the effect of transition to injection drug use on changes in sexual risk behavior during follow-up. Transition to injection drug use during follow-up was associated with increased likelihood of sexual risk behavior, especially for men. Harm reduction efforts that focus on preventing initiation or return to injection among non-injecting drug users may also ameliorate HIV sexual risk behaviors.

This article reviews the current issues and advancements in social network approaches to HIV prevention and care. Social network analysis can provide a method to understand health disparities in HIV rates, treatment access, and outcomes. Social network analysis is a valuable tool to link social structural factors to individual behaviors. Social networks provide an avenue for low-cost and sustainable HIV prevention interventions that can be adapted and translated into diverse populations. Social networks can be utilized as a viable approach to recruitment for HIV testing and counseling, HIV prevention interventions, optimizing HIV medical care, and medication adherence. Social network interventions may be face-to-face or through social media. Key issues in designing social network interventions are contamination due to social diffusion, network stability, density, and the choice and training of network members. There are also ethical issues involved in the development and implementation of social network interventions. Social network analyses can also be used to understand HIV transmission dynamics.

Background: Chronic hepatitis C (HCV) infection, defined as persistent RNA (viral load) for at least 6 months, accounts for up to 50% of all cirrhosis, end-stage liver disease and liver cancer cases. Moreover, elevated HCV viral load is consistently associated with high infectivity and poor therapy response. This study aims to identify modifiable behavioral correlates both chronic HCV infection and increases in viral load over time among injection drug users (IDUs)., Methods: Cross-sectional and longitudinal analyses were performed using self-interview and serological data from a prospective cohort study (2002-2006) among young (age 18-35), HIV-negative, HCV therapy-naïve IDUs (n=113) from metropolitan Chicago, Illinois, USA., Results: After adjustment for age, gender and race/ethnicity, using drugs measured or mixed in someone else's syringe (odds ratio=2.7, 95% confidence interval: 1.1, 6.7) was associated with chronic (n=75, 66%) versus resolved (n=38, 34%) HCV infection status. Among chronically-infected IDUs, injecting with a new, sterile syringe infrequently (<1/2 half the time when injecting) compared to frequently (1/2 the time or more when injecting) was associated with increases in viral load over time after adjusting for age, gender, race/ethnicity and time effects., Conclusions: Reductions in risky injection-related practices among young IDUs may ameliorate both the burden of chronic HCV infection-related liver disease and elevated viral load-related poor treatment response., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Background: Hepatitis C virus (HCV) infection prevalence among young injection drug users (IDUs) differs substantially between cities in the United States (U.S.)., Methods: Between 2002 and 2004, IDUs aged 15-30 were recruited for the Third Collaborative Injection Drug User Study in five U.S. cities using respondent-driven methods. Our cross-sectional study examined correlates and geographic distribution of prevalent HCV infection (HCV+) from the Baltimore (n=736) and Chicago (n=586) study sites. We evaluated baseline socio-demographic and behavioral data collected from computer-assisted self-interviews and serological antibody testing for human immunodeficiency virus (HIV) and hepatitis A, B, and C., Results: HCV prevalence was 53.0% in Baltimore and 13.7% in Chicago (p<0.0001). Baltimore compared to Chicago participants were significantly (p<0.05) more likely to be older, co-infected with HIV and other hepatitis viruses, reside in an urban area, inject primarily cocaine, inject in public settings, inject with used syringes and paraphernalia, and have been injecting longer; they were less likely to utilize syringe exchange programs. However, after accounting for socio-demographic and behavioral risk factors in multivariable logistic regression, city was the strongest predictor of HCV prevalence (Baltimore versus Chicago adjusted odds ratio=3.5 [95% confidence interval, 2.2-5.6]). Geospatial analyses showed that almost half of all HCV+ participants in Baltimore resided within a 5-mile urban area, while Chicago participants were dispersed across the metropolitan area., Conclusions: The disparate HCV prevalence between the two cities is only partially explained by individual-level factors. Future studies should examine the network configurations and injection partners' characteristics of young IDUs., (Copyright 2010 Elsevier Ireland Ltd. All rights reserved.)

Since the introduction of highly active antiretroviral therapy (HAART) and the subsequent increased life expectancy in HIV-infected persons, non-HIV-related diseases have become an important cause of morbidity and mortality. This cross-sectional study reports the prevalence of overweight and obesity, and sociodemographic, psychological, and substance use-related risk factors for elevated body mass index (BMI) among 2157 HIV-seropositive (HIV+) in comparison to 730 HIV-seronegative (HIV-) participants in the Women's Interagency HIV Study (WIHS). Separate univariable and multivariate linear regression analyses were completed for HIV+ and HIV- women. Our study revealed a similar proportion of obesity (body mass index [BMI] >or=30) among HIV+ (33%) and HIV- women (29%) (p = 0.12), as well as comparable median BMI (HIV+: 26.1 versus HIV-: 26.7, p = 0.16). HIV+ compared to HIV- women, respectively, were significantly (p < 0.01) older (median = 35.6 versus. 32.5), but similar (p = 0.97) by race/ethnicity (57% African American, 28% Hispanic, and 15% white for both). In multivariate models for both HIV+ and HIV- women, African American race/ethnicity was significantly (p < 0.05) associated with higher BMI, while higher quality of life score and illicit hard drug use were associated with lower BMI. Additionally, smoking, alcohol use, markers of advanced HIV infection (AIDS diagnosis, elevated HIV viral load, low CD4 count), and a history of antiretroviral therapy use (ART) were also associated with lower BMI among HIV+ women. In conclusion, risk factors for elevated BMI were similar for HIV+ and HIV- women in the WIHS. For HIV+ women, all markers of advanced HIV infection and ART use were additionally associated with lower BMI.

Background: The association of human leukocyte antigen (HLA) genes with the outcome of hepatitis C virus (HCV) infection may be modified by ethnic and geographical differences., Results: HLA-A, -C, -DRB1 and -DQB1 genotyping were performed in a Midwestern American cohort of 105 HCV infected subjects among which 49 cleared HCV infection and 56 had persistent viral infection. A new protective association of HLA-Cw*05 to HCV infection of all ethnic populations was identified (OR = 0.12, 95% CI = 0.01-0.97, P = 0.03). It was surprising that HLA-A*02 (P for interaction = 0.02) and HLA-DRB1*12 (P for interaction = 0.05) showed statistical interaction with race indicating opposite associations in Caucasians (OR = 2.74 for A*02 and 2.15 for DRB1*12) and non-Caucasians (OR = 0.41 for A*02 and 0.15 for DRB1*12). In addition, HLA-DRB1*01 (OR = 0.26), DQB1*05 (OR = 0.23) and the haplotype DRB1*01-DQB1*05 (OR = 0.19) showed strong associations with viral clearance in Caucasians. The protective associations of A*03 (OR = 0.20) and DQB1*03 (OR = 0.20) were exclusive to non-Caucasians. In contrast, DQB1*02 (OR = 2.56, 95% CI = 1.15-7.71, P = 0.02) and the haplotype DRB1*07-DQB1*02 (OR = 5.25, 95% CI = 1.04-26.6, P = 0.03) were risk markers in Caucasians., Conclusion: The associations of HLA-A*02 and HLA-DRB1*12 with HCV infection are opposite with different races. HLA-A*03, Cw*05, DRB1*01, DQB1*03 and DQB1*05 are associated with viral clearance while HLA-DRB1*07 and DQB1*02 are risk markers for viral persistence of HCV infection in Midwestern Americans. These results reveal ethnically and geographically different distribution of HLA-genes which are associated with the outcome of HCV infection.