Using Contact Patterns to Inform HIV Interventions in Persons Who Inject Drugs in Northern Vietnam

Transmission matrices used in epidemiologic modelling

Mixing matrices are included in infectious disease models to reflect transmission opportunities between population strata. These matrices were originally constructed on the basis of theoretical considerations and most of the early work in this area originates from research on sexually transferred diseases in the 80s, in response to AIDS. Later work in the 90s populated these matrices on the basis of survey data gathered to capture transmission risks for respiratory diseases. We provide an overview of developments in the construction of matrices for capturing transmission opportunities in populations. Such transmission matrices are useful for epidemiologic modelling to capture within and between stratum transmission and can be informed from theoretical mixing assumptions, informed by empirical evidence gathered through investigation as well as generated on the basis of data. Links to summary measures and threshold conditions are also provided.

Electronic dose monitoring identifies a high-risk subpopulation in the treatment of drug-resistant tuberculosis and HIV

BACKGROUND

In generalized drug-resistant tuberculosis (DR-TB) HIV epidemics, identifying subpopulations at high risk for treatment failure and loss to care is critically important to improve treatment outcomes and prevent amplification of drug resistance. We hypothesized that an electronic dose-monitoring (EDM) device could empirically identify adherence-challenged patients and that a mixed-methods approach would characterize treatment challenges.

METHODS

A prospective study of DR-TB HIV patients on antiretroviral therapy (ART) initiating bedaquiline-containing regimens in KwaZulu-Natal, South Africa. Separate EDM devices measured adherence for bedaquiline and ART. Patients with low adherence (<85%) to both bedaquiline and ART were identified as high-risk for poor outcomes. Baseline survey, study visit notes and focus group discussions characterized treatment challenges.

RESULTS

From December 2016-February 2018, 32 of 198 (16%) enrolled DR-TB HIV patients were identified as dual adherence-challenged. In a multivariate model including baseline characteristics, only receiving a disability grant was significantly associated with dual non-adherence at 6-months. Mixed-methods identified treatment barriers including, alcohol abuse, family conflicts, and mental health issues. Compared to adherent patients, dual-adherence challenged patients struggled to prioritize treatment and lacked support, and dual adherence-challenged patients experienced higher rates of detectable HIV viral load and mortality compared to more adherent patients.

CONCLUSION

EDM empirically identified a subpopulation of DR-TB HIV patients with dual adherence challenges early in treatment. Mixed-methods revealed intense psychosocial, behavioral, and structural barriers to care in this subpopulation. Our data supports developing differential, patient-centered, adherence support interventions focused on psychosocial and structural challenges for subpopulations of at-risk DR-TB HIV patients.

HCV incidence is associated with injecting partner age and HCV serostatus mixing in young adults who inject drugs in San Francisco

BACKGROUND

HCV incidence is increasing in the US, notably among younger people who inject drugs (PWID). In a cohort of young adult (age<30 years) PWID in San Francisco we examined whether 'injecting partner mixing' factors, i.e. age of partner and knowledge of their HCV serostatus, were associated with HCV transmission.

METHODS

In 448 susceptible PWID studied prospectively. All participants were asked to report characteristics and behaviors they engaged in with up to 3 injecting partners defined as "people whom you injected the most with" in the past month". These partnerships did not specify that drugs or injecting equipment was shared. HCV incidence was estimated by age of up to 3 injecting partners, categorized as: (i) all <30; (ii) mixed-age (<&≥30); and (iii) all ≥30 years and perceived knowledge of the HCV status of participants' injecting partners' HCV status. Interaction was evaluated between partnership age categories and perceived HCV status of partners.

RESULTS

Between 2006-2018, overall HCV incidence (/100 person years observation [pyo]) was 19.4 (95% CI: 16.4, 22.9). Incidence was highest in those with mixed-age partnerships: 28.5 (95% CI: 21.8, 37.1) and those whose partners were all <30 (23.9; 95% CI: 18.8, 30.4), and lowest if partners were ≥30 (7.5; 95% CI: 4.8, 11.8). In a multivariable analyses adjusting for age, sex (of index), injection frequency, and injection partnership 'monogamy', we found evidence for an interaction: the highest HCV incidence was seen in PWID whose partners were all <30 and who knew at least one of their partners was HCV-positive (58.9, 95% CI: 43.3, 80.0; p<0.01).

CONCLUSIONS

Younger injectors are more likely to acquire HCV from their similarly-aged peers, than older injecting partners. Protective seroadaptive behavior may contribute to reduce incidence. These findings can inform new HCV prevention approaches for young PWID needed to curb the HCV epidemic.

Regional differences between people who inject drugs in an HIV prevention trial integrating treatment and prevention (HPTN 074): a baseline analysis

INTRODUCTION

People who inject drugs (PWID) experience high HIV incidence and face significant barriers to engagement in HIV care and substance use treatment. Strategies for HIV treatment as prevention and substance use treatment present unique challenges in PWID that may vary regionally. Understanding differences in the risk structure for HIV transmission and disease progression among PWID is essential in developing and effectively targeting intervention strategies of HIV treatment as prevention.

METHODS

We present a baseline analysis of HIV Prevention Trials Network (HPTN) 074, a two-arm, randomized controlled trial among PWID in Indonesia (n = 258), Ukraine (n = 457) and Vietnam (n = 439). HPTN 074 was designed to determine the feasibility, barriers and uptake of an integrated intervention combining health systems navigation and psychosocial counselling for the early engagement of antiretroviral therapy (ART) and substance use treatment for PWID living with HIV. Discordant PWID networks were enrolled, consisting of an HIV-positive index and their HIV-negative network injection partner(s). Among the enrolled cohort of 1154 participants (502 index participants and 652 network partners), we examine regional differences in the baseline risk structure, including sociodemographics, HIV and substance use treatment history, and injection and sexual risk behaviours.

RESULTS

The majority of participants were male (87%), with 82% of the enrolled females coming from Ukraine. The overall mean age was 34 (IQR: 30, 38). Most commonly injected substances included illegally manufactured methadone in Ukraine (84.2%), and heroin in Indonesia (81.8%) and Vietnam (99.5%). Injection network sizes varied by region: median number of people with whom participants self-reported injecting drugs was 3 (IQR: 2, 5) in Indonesia, 5 (IQR: 3, 10) in Ukraine and 3 (IQR: 2, 4) in Vietnam. Hazardous alcohol use, assessed using the Alcohol Use Disorders Identification Test - Alcohol Consumption Questions (AUDIT-C), was prominent in Ukraine (54.7%) and Vietnam (26.4%). Reported sexual risk behaviours in the past month, including having two or more sex partners and giving/receiving money or drugs in exchange for sex, were uncommon among all participants and regions.

CONCLUSIONS

While regional differences in risk structure exist, PWID particularly in Ukraine need immediate attention for risk reduction strategies. Substantial regional differences in risk structure will require flexible, tailored treatment as prevention interventions for distinct PWID populations.