Sexual mixing patterns and heterosexual HIV transmission among African Americans in the southeastern United States

Sexual mixing in bisexual activity in male-male partnerships in Melbourne, Australia

Background The patterns of sexually transmitted infections (STIs) in populations may be influenced by the sexual mixing within the population. We aimed to investigate the assortative sexual mixing pattern by bisexuality in male-male partnerships. Methods This was a retrospective repeated cross-sectional study of men with mostly regular male partners attending the Melbourne Sexual Health Centre between 2011 and 2019. Data on sexual practices, including their sexual practices, presence of other male/female sex partners and the gender of sexual partners in the previous 3 and 12months, were collected using computer-assisted self-interview. We calculated the proportion of male partnerships where at least one man in the partnership reported a female sex partner. Results A total of 2056 male-male partnerships (i.e. 4112 individuals) with a median age of 29 years (IQR 25 to 35) were included. Overall, in 94.4% (1941/2056) of male-male partnerships both men had male partners only; however, in 5.5% (113/2056) of partnerships, one man had both male and female partners, and in 0.1% (2/2056) partnerships, both men had both male and female partners. No assortative relationship was found on the sexual mixing by bisexuality in male-male partnerships due to the low assortativity coefficient (r =0.006, 95% CI: -0.004 to 0.016). Conclusion One in 20 male-male partnerships had at least one man who had both male and female partners within the preceding year. Individuals were not selective by bisexuality, suggesting that partnerships of bisexual individuals are mixed proportionately to the distribution of their characteristics. Still, these sexual mixing practices may affect STI transmission dynamics.

Protocol for WeExPAnd: a prospective, mixed-methods pilot demonstration study to increase access to pre-exposure prophylaxis among women vulnerable to HIV infection in the Southern USA

INTRODUCTION

African American women (AA), particularly those living in the Southeastern USA, experience disproportionately high rates of HIV infection. Pre-exposure prophylaxis (PrEP) is a highly effective HIV prevention tool that may circumvent barriers to traditional HIV prevention tools, such as condom use; however, very little is known about how to improve PrEP access and uptake among AA women who may benefit from PrEP use. This project aims to understand how to increase PrEP access among AA women in the rural Southern USA, which may ultimately affect HIV incidence in this population.

METHODS AND ANALYSIS

The goal of the current study is to systematically adapt a patient-provider communication tool to increase PrEP uptake among AA women receiving care at a federally qualified health centre in Alabama. We will use an iterative implementation process, by assessing the feasibility, acceptability and preliminary impact of the tool on PrEP uptake, using a pilot preintervention/postintervention design (N=125). We will evaluate women's reasons for declining a referral to a PrEP provider, reasons for incomplete referrals, reasons for not initiating PrEP after a successful referral and ongoing PrEP use at 3 and 12 months after PrEP initiation among our sample. The proposed work will significantly contribute to our understanding of factors impacting PrEP uptake and use among AA women, particularly in underserved areas in the Deep South that are heavily impacted by the HIV epidemic and experience worse HIV-related health outcomes relative to other areas in the USA.

ETHICS AND DISSEMINATION

This protocol has been approved by the Institutional Review Board (IRB) at University of Alabama at Birmingham (Birmingham, AL; protocol 300004276). All participants will review a detailed informed consent form approved by the IRB and will provide written or verbal informed consent prior to enrolment. Results will be disseminated through peer-reviewed manuscripts, reports, and local, national and international presentations.

TRIAL REGISTRATION NUMBER

NCT04373551.

Social divisions and risk perception drive divergent epidemics and large later waves

During infectious disease outbreaks, individuals may adopt protective measures like vaccination and physical distancing in response to awareness of disease burden. Prior work showed how feedbacks between epidemic intensity and awareness-based behaviour shape disease dynamics. These models often overlook social divisions, where population subgroups may be disproportionately impacted by a disease and more responsive to the effects of disease within their group. We develop a compartmental model of disease transmission and awareness-based protective behaviour in a population split into two groups to explore the impacts of awareness separation (relatively greater in- vs. out-group awareness of epidemic severity) and mixing separation (relatively greater in- vs. out-group contact rates). Using simulations, we show that groups that are more separated in awareness have smaller differences in mortality. Fatigue (i.e. abandonment of protective measures over time) can drive additional infection waves that can even exceed the size of the initial wave, particularly if uniform awareness drives early protection in one group, leaving that group largely susceptible to future infection. Counterintuitively, vaccine or infection-acquired immunity that is more protective against transmission and mortality may indirectly lead to more infections by reducing perceived risk of infection and therefore vaccine uptake. Awareness-based protective behaviour, including awareness separation, can fundamentally alter disease dynamics. Social media summary: Depending on group division, behaviour based on perceived risk can change epidemic dynamics & produce large later waves.

The influence of social relationships on PrEP attitudes among women with incarceration experience in the Southeastern USA

Women who have experienced incarceration face a disproportionately high risk of acquiring HIV. Despite efficacy of pre-exposure prophylaxis (PrEP) for HIV, very few women with incarceration histories are using PrEP. Our objective was to learn how sexual, drug-use and social relationships shape decisions about PrEP among women who have experienced incarceration. We used an inductive approach to analyse data from four focus groups undertaken with women who had previously experienced incarceration recruited from three community-based organisations. We identified public policy (medical distrust, lack of prevention in prisons and jails, and cost and coverage of PrEP); community (incarceration stigma, gossip as prevention); social and sexual network (positive peer and parenting relationships, distrust of sexual partners, and networks as a source of risk); and individual-level (active addiction or recovery, change after incarceration, and medical concerns) factors influencing the use of PrEP. Actions and interventions to improve PrEP uptake among women who have experienced incarceration must take account of the multilevel context of HIV prevention decisions.

Human papillomavirus vaccine coverage in male-male partnerships attending a sexual health clinic in Melbourne, Australia

We aimed to investigate the sexual mixing by human papillomavirus (HPV) vaccination status in male-male partnerships and estimate the proportion of male-male partnerships protected against HPV. We analyzed male-male partnerships attending the Melbourne Sexual Health Center between 2018 and 2019. Data on self-reported HPV vaccination status were collected. Newman’s assortativity coefficient was used to examine the sexual mixing by HPV vaccination status. Assortativity refers to the tendency of individuals to have partners with similar characteristics (i.e. same vaccination status). Of 321 male-male partnerships where both men reported their HPV vaccination status, 52.6% (95% CI: 47.0–58.2%) partnerships had both men vaccinated, 32.1% (95% CI: 27.0–37.5%) partnerships had only one man vaccinated, and 15.3% (95% CI: 11.5–19.7%) had both men unvaccinated. The assortativity on HPV vaccination status was moderate (assortativity coefficient = 0.265, 95% CI: 0.196–0.335). There were about 15% of male-male partnerships where both men were not protected against HPV. Interventions targeting vaccinated individuals to encourage their unvaccinated partners to be vaccinated might increase the HPV vaccine coverage.

Sexual Mixing and HIV Transmission Potential Among Greek Men Who have Sex with Men: Results from SOPHOCLES

HIV incidence among men who have sex with men (MSM) in Greece remains unchanged despite effective response to a recent outbreak among people who inject drugs (PWID). Network factors are increasingly understood to drive transmission in epidemics. The primary objective of the study was to characterize MSM in Greece, their sexual behaviors, and sexual network mixing patterns. We investigated the relationship between serostatus, sexual behaviors, and self-reported sex networks in a sample of MSM in Athens, Greece, generated using respondent driven sampling. We estimated mixing coefficients (r) based on survey-generated egonets. Additionally, multiple logistic regression was used to estimate adjusted odds ratios (AOR) and to assess relationships between serostatus, sexual behaviors, and sociodemographic indicators. A sample of 1,520 MSM participants included study respondents (n = 308) and their network members (n = 1,212). Mixing based on serostatus (r = 0.12, σr = 0.09-0.15) and condomless sex (r = 0.11, σr = 0.07-0.14) was random. However, mixing based on sex-drug use was highly assortative (r = 0.37, σr = 0.32-0.42). This study represents the first analysis of Greek MSM sexual networks. Our findings highlight protective behavior in two distinct network typologies. The first typology mixed assortatively based on serostatus and sex-drug use and was less likely to engage in condomless sex. The second typology mixed randomly based on condomless sex but was less likely to engage in sex-drug use. These findings support the potential benefit of HIV prevention program scale-up for this population including but not limited to PrEP.

Reducing HIV Risk Behaviors Among Black Women Living With and Without HIV/AIDS in the U.S.: A Systematic Review

This systematic review provides an examination of the status of HIV/AIDS prevention interventions for Black, heterosexual women in the U.S. from 2012 to 2019. Using PRISMA guidelines, 28 interventions were identified. Over half of the interventions were: conducted in the southern region of the U.S.; evaluated using a randomized controlled trial; focused on adults; used a group-based intervention delivery; were behaviorally focused and theoretically driven. None included biomedical strategies of PrEP, nPEP, and TasP. Few interventions included adolescent or aging Black women; none included their sex/romantic partners. Future studies dedicated to addressing the specific needs of subpopulations of Black, heterosexual women may provide opportunities to expand and/or tailor current and future HIV/AIDS prevention interventions, including offering participants with options to choose which, and the level of involvement, of their sex/romantic partner(s) in their sexual health decision-making. While strides to improve HIV prevention efforts with Black, heterosexual women have occurred, more is needed.

Lost and found: applying network analysis to public health contact tracing for HIV

Infectious disease surveillance is often case-based, focused on people diagnosed and their contacts in a predefined time window, and treated as independent across infections. Network analysis of partners and contacts joining multiple investigations and infections can reveal social or temporal trends, providing opportunities for epidemic control within broader networks. We constructed a sociosexual network of all HIV and early syphilis cases and contacts investigated among residents of 11 contiguous counties in North Carolina over a two-year period (2012-2013). We anchored the analysis on new HIV diagnoses ("indexes"), but also included nodes and edges from syphilis investigations that were within the same network component as any new HIV index. After adding syphilis investigations and deduplicating people included in multiple investigations (entity resolution), the final network comprised 1470 people: 569 HIV indexes, 700 contacts to HIV indexes who were not also new cases themselves, and 201 people who were either indexes or contacts in eligible syphilis investigations. Among HIV indexes, nearly half (48%; n = 273) had no located contacts during single-investigation contact tracing, though 25 (9%) of these were identified by other network members and thus not isolated in the final multiple investigation network. Constructing a sociosexual network from cases and contacts across multiple investigations mitigated some effects of unobserved partnerships underlying the HIV epidemic and demonstrated the HIV and syphilis overlap in these networks.

Laboratory Perspective on Racial Disparities in Sexually Transmitted Infections

BACKGROUND

Rates of sexually transmitted infections (STI) have risen steadily in recent years, and racial and ethnic minorities have borne the disproportionate burden of STI increases in the United States. Historical inequities and social determinants of health are significant contributors to observed disparities and affect access to diagnostic testing for STI.

CONTENT

Public health systems rely heavily on laboratory medicine professionals for diagnosis and reporting of STI. Therefore, it is imperative that clinicians and laboratory professionals be familiar with issues underlying disparities in STI incidence and barriers to reliable diagnostic testing. In this mini-review, we will summarize contributors to racial/ethnic disparity in STI, highlight current epidemiologic trends for gonorrhea, chlamydia, and syphilis, discuss policy issues that affect laboratory and public health funding, and identify specific analytic challenges for diagnostic laboratories.

SUMMARY

Racial and ethnic disparities in STI in the US are striking and are due to complex interactions of myriad social determinants of health. Budgetary cuts for laboratory and public health services and competition for resources during the COVID-19 pandemic are major challenges. Laboratory professionals must be aware of these underlying issues and work to maximize efforts to ensure equitable access to diagnostic STI testing for all persons, particularly those most disproportionately burdened by STI.

Factors Associated With Human Immunodeficiency Virus Infections Linked in Genetic Clusters But Disconnected in Partner Tracing

BACKGROUND

Successful partner notification can improve community-level outcomes by increasing the proportion of persons living with human immunodeficiency virus (HIV) who are linked to HIV care and virally suppressed, but it is resource intensive. Understanding where HIV transmission pathways may be undetected by routine partner notification may help improve case finding strategies.

METHODS

We combined partner notification interview and HIV sequence data for persons diagnosed with HIV in Wake County, NC in 2012 to 2013 to evaluate partner contact networks among persons with HIV pol gene sequences 2% or less pairwise genetic distance. We applied a set of multivariable generalized estimating equations to identify correlates of disparate membership in genetic versus partner contact networks.

RESULTS

In the multivariable model, being in a male-male pair (adjusted odds ratio [AOR], 16.7; P = 0.01), chronic HIV infection status (AOR, 4.5; P < 0.01), and increasing percent genetic distance between each dyad member's HIV pol gene sequence (AOR, 8.3 per each 1% increase, P < 0.01) were all associated with persons with HIV clustering but not being identified in the partner notification network component. Having anonymous partners or other factors typically associated with risk behavior were not associated.

CONCLUSIONS

Based on genetic networks, partnerships which may be stigmatized, may have occurred farther back in time or may have an intervening partner were more likely to be unobserved in the partner contact network. The HIV genetic cluster information contributes to public health understanding of HIV transmission networks in these settings where partner identifying information is not available.

Advances in research of HIV transmission networks

Transmission network analysis is a crucial evaluation tool aiming to explore the characteristics of the human immunodeficiency virus epidemic, develop evidence-based prevention strategies, and contribute to various areas of human immunodeficiency virus/acquired immunodeficiency syndrome prevention and control. Over recent decades, transmission networks have made tremendous strides in terms of modes, methods, applications, and various other aspects. Transmission network methods, including social, sexual, and molecular transmission networks, have played a pivotal role. Each transmission network research method has its advantages, as well as its limitations. In this study, we established a systematic review of these aforementioned transmission networks with respect to their definitions, applications, limitations, recent progress, and synthetic applications.

HIV seroconcordance among heterosexual couples in rural KwaZulu-Natal, South Africa: a population-based analysis

INTRODUCTION

High levels of HIV seroconcordance at the population level reduce the potential for effective HIV transmission. However, the level of HIV seroconcordance is largely unknown among heterosexual couples in sub-Saharan Africa. We aimed to quantify the population level HIV seroconcordance in stable heterosexual couples in rural South Africa.

METHODS

We followed adults (≥15 years old) using a population-based, longitudinal and open surveillance system in KwaZulu-Natal, South Africa, from 2003 to 2016. Sexual partnerships and HIV status were confirmed via household surveys and annual HIV surveillance. We calculated the proportions of HIV seroconcordance and serodiscordance in stable sexual partnerships and compared them to the expected proportions under the assumption of random mixing using individual-based microsimulation models. Among unpartnered individuals, we estimated the incidence rates and hazard of sexual partnership formation with HIV-positive or HIV-negative partners by participants' own time-varying HIV status. Competing risks survival regressions were fitted adjusting for sociodemographic and clinical factors. We also calculated Newman's assortativity coefficients.

RESULTS

A total of 18,341 HIV-negative and 11,361 HIV-positive individuals contributed 154,469 person-years (PY) of follow-up. Overall, 28% of the participants were in stable sexual partnerships. Of the 677 newly formed stable sexual partnerships, 7.7% (95% CI: 5.8 to 10.0) were HIV-positive seroconcordant (i.e. both individuals in the partnership were HIV-positive), which was three times higher than the expected proportion (2.3%) in microsimulation models based on random mixing. The incidence rates of sexual partnership formation were 0.54/1000PY with HIV-positive, 1.12/1000PY with HIV-negative and 2.65/1000PY with unknown serostatus partners. HIV-positive individuals had 2.39 (95% CI: 1.43 to 3.99) times higher hazard of forming a sexual partnership with an HIV-positive partner than did HIV-negative individuals after adjusting for age, opposite-sex HIV prevalence (by 5-years age groups), HIV prevalence in the surrounding community, ART coverage and other sociodemographic factors. Similarly, forming a sexual partnership with an HIV-negative partner was 1.47 (95% CI: 1.01 to 2.14) times higher in HIV-negative individuals in the adjusted model. Newman's coefficient also showed that assortativity by participant and partner HIV status was moderate (r = 0.35).

CONCLUSIONS

A high degree of population level HIV seroconcordance (both positive and negative) was observed at the time of forming new sexual partnerships. Understanding factors driving these patterns may help the development of strategies to bring the HIV epidemic under control.

Incarceration and Number of Sexual Partners After Incarceration Among Vulnerable US Women, 2007-2017

Objectives. To examine whether women's incarceration increases numbers of total and new sexual partners.Methods. US women with or at risk for HIV in a multicenter cohort study answered incarceration and sexual partner questions semiannually between 2007 and 2017. We used marginal structural models to compare total and new partners at visits not following incarceration with all visits following incarceration and visits immediately following incarceration. Covariates included demographics, HIV status, sex exchange, drug or alcohol use, and housing instability.Results. Of the 3180 participants, 155 were incarcerated. Women reported 2 partners, 3 or more partners, and new partners at 5.2%, 5.2%, and 9.3% of visits, respectively. Relative to visits not occurring after incarceration, odds ratios were 2.41 (95% confidence interval [CI] = 1.20, 4.85) for 2 partners, 2.03 (95% CI = 0.97, 4.26) for 3 or more partners, and 3.24 (95% CI = 1.69, 6.22) for new partners at visits immediately after incarceration. Odds ratios were similar for all visits following incarceration.Conclusions. Women had more total partners and new partners immediately and at all visits following incarceration after confounders and loss to follow-up had been taken into account.

Interaction Patterns of Men Who Have Sex With Men on a Geosocial Networking Mobile App in Seven United States Metropolitan Areas: Observational Study

BACKGROUND

The structure of the sexual networks and partnership characteristics of young black men who have sex with men (MSM) may be contributing to their high risk of contracting HIV in the United States. Assortative mixing, which refers to the tendency of individuals to have partners from one's own group, has been proposed as a potential explanation for disparities.

OBJECTIVE

The objective of this study was to identify the age- and race-related search patterns of users of a diverse geosocial networking mobile app in seven metropolitan areas in the United States to understand the disparities in sexually transmitted infection and HIV risk in MSM communities.

METHODS

Data were collected on user behavior between November 2015 and May 2016. Data pertaining to behavior on the app were collected for men who had searched for partners with at least one search parameter narrowed from defaults or used the app to send at least one private chat message and used the app at least once during the study period. Newman assortativity coefficient (R) was calculated from the study data to understand assortativity patterns of men by race. Pearson correlation coefficient was used to assess assortativity patterns by age. Heat maps were used to visualize the relationship between searcher's and candidate's characteristics by age band, race, or age band and race.

RESULTS

From November 2015 through May 2016, there were 2,989,737 searches in all seven metropolitan areas among 122,417 searchers. Assortativity by age was important for looking at the profiles of candidates with correlation coefficients ranging from 0.284 (Birmingham) to 0.523 (San Francisco). Men tended to look at the profiles of candidates that matched their race in a highly assortative manner with R ranging from 0.310 (Birmingham) to 0.566 (Los Angeles). For the initiation of chats, race appeared to be slightly assortative for some groups with R ranging from 0.023 (Birmingham) to 0.305 (Los Angeles). Asian searchers were most assortative in initiating chats with Asian candidates in Boston, Los Angeles, New York, and San Francisco. In Birmingham and Tampa, searchers from all races tended to initiate chats with black candidates.

CONCLUSIONS

Our results indicate that the age preferences of MSM are relatively consistent across cities, that is, younger MSM are more likely to be chatted with and have their profiles viewed compared with older MSM, but the patterns of racial mixing are more variable. Although some generalizations can be made regarding Web-based behaviors across all cities, city-specific usage patterns and trends should be analyzed to create targeted and localized interventions that may make the most difference in the lives of MSM in these areas.

The multiplex social environments of young Black men who have sex with men: How online and offline social structures impact HIV prevention and sex behavior engagement

In the United States, young Black men who have sex with men (YBMSM) remain disproportionately affected by HIV. The social networks in which YBMSM are embedded are generally understood to be critical factors in understanding their vulnerability. In this study, we acknowledge the relational richness of YBMSMs' social environments (what we define as multiplexity) and their increasing prioritization of online social networking sites (SNS). Specifically, we investigate whether protective and/or risky features of YBMSMs' Facebook friendships and group affiliations are related to their HIV prevention and sex behavior engagement, while also accounting for features of their offline confidant (or support) and sex networks. Using data from a population-based cohort study of YBMSM living in Chicago (N=268), we perform a series of multiple logistic regression analyses to examine associations between features of YBMSMs' Facebook, confidant, and sexual networks with three prevention outcomes and three sex behavior outcomes, while also controlling for factors at the individual and structural levels. Results show that network features play a more significant role in predicting engagement in sex behaviors than prevention behaviors. Specifically, having more confidants, having confidants who are family members, meeting sex partners online, having more YBMSM Facebook friends, belonging to Facebook groups with an LGBTQ focus, and having greater subject diversity in one's Facebook group affiliations were significantly associated with one or more sex behavior outcomes. We conclude with a discussion of the implications of our findings for HIV prevention intervention efforts.

Decreasing HIV transmissions to African American women through interventions for men living with HIV post-incarceration: An agent-based modeling study

Background

Incarceration and HIV disproportionately impact African American communities. The mass incarceration of African American men is hypothesized to increase HIV acquisition risk for African American women. Interventions optimizing HIV care engagement and minimizing sexual risk behaviors for men living with HIV post-incarceration may decrease HIV incidence.

Methods

Using an agent-based model, we simulated a sexual and injection drug using network representing the African American population of Philadelphia. We compared intervention strategies for men living with HIV post-incarceration by the number of averted HIV transmissions to women within the community. Three interventions were evaluated: a 90-90-90 scenario scaling up HIV testing, ART provision, and ART adherence; a behavioral intervention decreasing sexual risk behaviors; and a combination intervention involving both.

Results

The status quo scenario projected 2,836 HIV transmissions to women over twenty years. HIV transmissions to women decreased by 29% with the 90-90-90 intervention, 23% with the behavioral intervention, and 37% with both. The number of men living with HIV receiving the intervention needed in order to prevent a single HIV transmission ranged between 6 and 10.

Conclusion

Interventions to improve care engagement and decrease sexual risk behaviors post-incarceration for men living with HIV have the potential to decrease HIV incidence within African American heterosexual networks.

Inferring the age difference in HIV transmission pairs by applying phylogenetic methods on the HIV transmission network of the Swiss HIV Cohort Study

Age-mixing patterns are of key importance for understanding the dynamics of human immunodeficiency virus (HIV)-epidemics and target public health interventions. We use the densely sampled Swiss HIV Cohort Study (SHCS) resistance database to study the age difference at infection in HIV transmission pairs using phylogenetic methods. In addition, we investigate whether the mean age difference of pairs in the phylogenetic tree is influenced by sampling as well as by additional distance thresholds for including pairs. HIV-1 pol-sequences of 11,922 SHCS patients and approximately 240,000 Los Alamos background sequences were used to build a phylogenetic tree. Using this tree, 100 per cent down to 1 per cent of the tips were sampled repeatedly to generate pruned trees (N = 500 for each sample proportion), of which pairs of SHCS patients were extracted. The mean of the absolute age differences of the pairs, measured as the absolute difference of the birth years, was analyzed with respect to this sample proportion and a distance criterion for inclusion of the pairs. In addition, the transmission groups men having sex with men (MSM), intravenous drug users (IDU), and heterosexuals (HET) were analyzed separately. Considering the tree with all 11,922 SHCS patients, 2,991 pairs could be extracted, with 954 (31.9 per cent) MSM-pairs, 635 (21.2 per cent) HET-pairs, 414 (13.8 per cent) IDU-pairs, and 352 (11.8 per cent) HET/IDU-pairs. For all transmission groups, the age difference at infection was significantly (P < 0.001) smaller for pairs in the tree compared with randomly assigned pairs, meaning that patients of similar age are more likely to be pairs. The mean age difference in the phylogenetic analysis, using a fixed distance of 0.05, was 9.2, 9.0, 7.3 and 5.6 years for MSM-, HET-, HET/IDU-, and IDU-pairs, respectively. Decreasing the cophenetic distance threshold from 0.05 to 0.01 significantly decreased the mean age difference. Similarly, repeated sampling of 100 per cent down to 1 per cent of the tips revealed an increased age difference at lower sample proportions. HIV-transmission is age-assortative, but the age difference of transmission pairs detected by phylogenetic analyses depends on both sampling proportion and distance criterion. The mean age difference decreases when using more conservative distance thresholds, implying an underestimation of age-assortativity when using liberal distance criteria. Similarly, overestimation of the mean age difference occurs for pairs from sparsely sampled trees, as it is often the case in sub-Saharan Africa.

Human papillomavirus vaccination and the role of herd effects in future cancer control planning: a review

INTRODUCTION

Vaccine herd effects are the indirect protection that vaccinated persons provide to those who remain susceptible to infection, due to the reduced transmission of infections. Herd effects have been an important part of the discourse on how to best implement human papillomavirus (HPV) vaccines and prevent HPV-related diseases.

AREAS COVERED

In this paper, we review the theory of HPV vaccine herd effects derived from mathematical models, give an account of observed HPV vaccine herd effects worldwide, and examine the implications of vaccine herd effects for future cervical cancer screening efforts.

EXPERT COMMENTARY

HPV vaccine herd effects improve the cost-effectiveness of vaccinating preadolescent girls, but contribute to making gender-neutral vaccination less economically efficient. Vaccination coverage and sexual mixing patterns by age are strong determinants of herd effects. Many countries worldwide are starting to observe reductions in HPV-related outcomes likely attributable to herd effects, most notably declining anogenital warts in young men, and declining HPV-16/18 infection prevalence in young unvaccinated women. Policy makers making recommendations for cervical cancer screening will have to consider HPV vaccination coverage and herd effects, as these will affect the positive predictive value of screening and the risk of cervical cancer in unvaccinated women.

Racial Inequities in HIV Prevalence and Composition of Risk Networks Among People Who Inject Drugs in HIV Prevention Trial Network 037

BACKGROUND

HIV prevention interventions in the United States have failed to eliminate racial inequities. Here, we evaluate factors associated with racial inequities in HIV prevalence among people who inject drugs using HIV Prevention Trial Network 037 data.

METHODS

We measured racial homophily (ie, all members share the same race), being in an HIV+ network (network with ≥1 HIV+ member), and drug and sex risk behaviors. A 2-level logistic regression with a random intercept evaluated the association between being in an HIV+ network and race adjusting for individual-level and network-level factors.

RESULTS

Data from 232 index participants and 464 network members were included in the analysis. Racial homophily was high among blacks (79%) and whites (70%); 27% of all-black, 14% of all-white, and 23% of racially mixed networks included HIV+ members. Sex risk was similar across networks, but needle sharing was significantly lower in all-black (23%) compared with all-white (48%) and racially mixed (46%) networks. All-black [adjusted odds ratio (AOR), 3.6; 95% confidence interval (CI), 1.4 to 9.5] and racially mixed (AOR, 2.0; 95% CI: 1.1 to 3.7) networks were more likely to include HIV+ network members; other factors associated with being in HIV+ network included homelessness (AOR, 2.0; 95% CI, 1.2 to 3.2), recent incarceration (AOR, 0.4; 95% CI, 0.2 to 0.7), and cocaine injection (AOR, 1.7; 95% CI, 1.0 to 2.7). Risk behaviors were not associated with being in an HIV+ network.

CONCLUSION

Despite having lower drug risk behavior, all-black networks disproportionately included HIV+ members. HIV prevention interventions for people who inject drugs need to go beyond individual risk and consider the composition of risk networks.

Assortativity and Mixing by Sexual Behaviors and Sociodemographic Characteristics in Young Adult Heterosexual Dating Partnerships

BACKGROUND

Assortative sexual mixing, the tendency for individuals to choose partners with similar characteristics to themselves, may be an important contributor to the unequal distribution of sexually transmitted infections in populations. We analyzed the tendency for assortative mixing on demographic and sexual behaviors characteristics in newly formed young adults dating partnerships.

METHODS

Women aged 18 to 24 years and their male sexual partners of no more than 6 months were recruited during 2005 to 2010 at universities in Montreal, Canada. New dating partners were also prospectively recruited during the 2-year follow-up. We used Spearman and Newman coefficients to examine correlations between partners' demographic characteristics and sexual behaviors, and multivariable logistic modeling to determine which characteristics were assortative.

RESULTS

Participants in 502 recruited partnerships were assortative on age (Spearman P = 0.60), smoking behavior (P = 0.43), ethnicity (Newman coefficient=0.39), lifetime number of sexual partners (P = 0.36), sex partner acquisition rates (P = 0.22), gap length between partnerships (P = 0.20), and on whether they had concurrent partners (P = 0.33). Partners were assortative on number of lifetime partners, sexual partner acquisition rates, concurrency, and gap length between partnerships even after adjustment for demographic characteristics. Reported condom use was correlated between initial and subsequently recruited partners (P = 0.35). There was little correlation between the frequencies of vaginal/oral/digital/anal sex between subsequent partnerships.

CONCLUSIONS

Dating partnerships were substantially assortative on various sexual behaviors as well as demographic characteristics. Though not a representative population sample, our recruitment of relatively new partnerships reduces survivor bias inherent to cross-sectional surveys where stable long-term partnerships are more likely to be sampled.

Optimizing Delivery of HIV Preexposure Prophylaxis for Women in the United States

Preexposure prophylaxis (PrEP) is a highly effective HIV prevention method; however, it is underutilized among women who are at risk for acquisition of HIV. Women comprise one in five HIV diagnoses in the United States, and significant racial disparities in new HIV diagnoses persist. The rate of new HIV diagnoses among black and African American women in 2015 was 16 times greater than that of white women. These disparities highlight the importance of HIV prevention strategies for women, including the use of PrEP. PrEP is the first highly effective HIV prevention method available to women that is entirely within their control. However, because so few women who may benefit from PrEP are aware of it, few women's healthcare providers offer PrEP to their patients, PrEP has not yet achieved its potential to reduce HIV infections in women. This article describes individual and systemic barriers for women related to the uptake of PrEP services; explains how providers can identify women at risk for HIV; reviews how to provide PrEP to women; and outlines client-centered models for HIV prevention services. Better access to culturally acceptable and affordable medical and social services may offer support to women for consistent and ongoing use of PrEP. This discussion may be used to inform HIV prevention activities for women and guide interventions to decrease racial/ethnic disparities in rates of HIV infection among US women.

Sex Behaviors as Social Cues Motivating Social Venue Patronage Among Young Black Men Who Have Sex with Men

HIV prevention programs often focus on the physical social venues where men who have sex with men (MSM) frequent as sites where sex behaviors are assumed to be practiced and risk is conferred. But, how exactly these behaviors influence venue patronage is not well understood. In this study, we present a two-mode network analysis that determines the extent that three types of sex behaviors-condomless sex, sex-drug use, and group sex-influence the patronage of different types of social venues among a population sample of young Black MSM (YBMSM) (N = 623). A network analytic technique called exponential random graph modeling was used in a proof of concept analysis to verify how each sex behavior increases the likelihood of a venue patronage tie when estimated as either: (1) an attribute of an individual only and/or (2) a shared attribute between an individual and his peers. Findings reveal that sex behaviors, when modeled only as attributes possessed by focal individuals, were no more or less likely to affect choices to visit social venues. However, when the sex behaviors of peers were also taken into consideration, we learn that individuals were statistically more likely in all three behavioral conditions to go places that attracted other MSM who practiced the same behaviors. This demonstrates that social venues can function as intermediary contexts in which relationships can form between individuals that have greater risk potential given the venues attraction to people who share the same risk tendencies. As such, structuring interventions around these settings can be an effective way to capture the attention of YBMSM and engage them in HIV prevention.

Social determinants of adult sex ratios and racial/ethnic disparities in transmission of HIV and other sexually transmitted infections in the USA

In Black population centres in the USA, adult sex ratios (ASRs) are strongly female-biased primarily due to high male incarceration and early mortality rates. I explore the system of social determinants that shape these ASRs, and describe their apparent consequences. Evidence suggests that female-biased ASRs play a role, along with racial residential segregation, to increase mixing between core and peripheral members of sexual networks, facilitating transmission of human immunodeficiency virus and other sexually transmitted infections. Unique historical factors underlie Black male incarceration and mortality rates in the USA, making comparisons with other groups or other countries challenging.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

Exploring Factors Associated with Declining HIV Diagnoses Among African American Females

HIV diagnoses among females in the USA declined 40% during 2005-2014 with the largest decline (42%) among Black/African Americans. African American females remain disproportionately affected. We explored contributions of STD rates and sexual risk behaviors among African American females, HIV diagnoses among potential male partners, and sexual risk behaviors and viral suppression rates among HIV-positive potential male partners to declining rates of HIV diagnoses among African American females. Results suggest temporal trends in the factors that increase HIV infectiousness and transmissibility within sexual networks, i.e., decreases in rates of other sexually transmitted infections among African American females, decreases in HIV diagnoses among potential male partners, and increases in viral suppression among heterosexual and bisexual HIV-positive potential male partners in care, may explain the decline. Findings highlight a need for future research that provides context to the sexual risk behaviors and sexual network factors in order to continue progress.

Sexual Risk and Protective Behaviors Among Reproductive-Aged Women in the United States

BACKGROUND

In 2014, women represented 19% of HIV diagnoses in the United States. Of these, 78% were among black women and Latinas. Sexual risk behaviors-for example concurrent sex partnerships, nonmonogamous sex partners, and inconsistent condom use-are associated with increased HIV transmission and prevalence; these behaviors have been understudied, collectively, in women.

METHODS

To examine HIV-related sexual risk behaviors among sexually active women aged 18-44 years by race/ethnicity and over time, we used data from the 2006-2008, 2008-2010, and 2011-2013 cycles of the National Survey of Family Growth. We estimated weighted percentages and performed logistic regression to measure adjusted prevalence ratios (aPR) and 95% confidence intervals (CI) for associations between selected behaviors and sociodemographic covariates.

RESULTS

Among 13,588 women, 1.1% reported concurrent sex partnerships, 10.3% reported male partners whom they perceived were nonmonogamous, and 21.1% reported using a condom at either last vaginal or anal sex. Black women (aPR = 1.52; CI = 1.36-1.71) and Latinas (aPR = 1.29; CI = 1.14-1.47) were more likely to report condom use at either last vaginal or anal sex compared with white women. However, black women were also more likely to report concurrent opposite-sex partnerships (aPR = 2.44; CI = 1.57-3.78) and perceived nonmonogamous sex partners (aPR = 1.33; CI = 1.14-1.56) compared with white women.

CONCLUSIONS

Improved HIV behavioral risk-reduction strategies are needed for women. Black women could benefit from interventions that address partnership concurrency. For black women and Latinas, who are more likely to use condoms, further examination of broader social and structural factors as contributors to racial/ethnic gaps are warranted and vital for understanding and decreasing HIV-related disparities.

Intersectional Epistemologies of Ignorance: How Behavioral and Social Science Research Shapes What We Know, Think We Know, and Don't Know About U.S. Black Men's Sexualities

Epistemologies of ignorance describe how ignorance influences the production of knowledge. Advancing an intersectional epistemologies of ignorance approach that examines how conscious (or unconscious) ignorance about racism, heterosexism, and classism shapes empirical knowledge about Black men's sexualities, we conducted a critical review of the behavioral and social science research on U.S. Black men, ages 18 and older, for two time frames: pre-1981 and the most recent decade, 2006-2016. Our search yielded 668 articles, which we classified into five categories: sexual violence, sexual experiences and expressions, sexual identities, cultural and social-structural influences, and sexual health and sexual risk. We found that most of the research, particularly pre-1981, centered the experiences of White heterosexual men as normative and implicitly constructed Black men as hypersexual or deviant. Most of the research also color-blinded White privilege and ignored how racism, heterosexism, and classism structured Black men's inequities. We also found notable exceptions to these trends. Black men who are gay, bisexual, or who have sex with men, and research on HIV risk were prominent in the past decade, as was research that emphasized the social-structural (e.g., poverty, heterosexism, racism) and cultural (e.g., masculinity, religion) contexts of Black men's lives and sexualities. We provide 10 recommendations to avoid intersectional epistemic ignorance in future research.

Pre-exposure prophylaxis prescribing and retention in care among heterosexual women at a community-based comprehensive sexual health clinic

In the United States, heterosexual women account for 20% of new HIV infections. As a user-controlled HIV prevention method, pre-exposure prophylaxis (PrEP) has substantial potential to reduce new infections among women. However, among women, PrEP is vastly underutilized. To guide efforts to increase women-at-risk's PrEP use, we sought to describe the characteristics of women prescribed PrEP as well as their retention in PrEP care. We conducted a chart review of women who received care at a comprehensive sexual health clinic within a large urban health care system. Referral sources included the health care system's clinics and HIV testing program, as well as local community-based organizations. From 1 December 2014 to 5 August 2016, 554 women received care at the clinic. During this period, 21 heterosexual women (3.8%) received at least one prescription for daily oral PrEP. For women prescribed PrEP, median age was 35 years old (range: 20-52). The majority (66.7%) were either Latina or non-Latina Black and most (81.2%) had public health insurance. The most common PrEP indication was being in a known sero-discordant partnership (85.7%). Of women in such partnerships, 83.3% reported their male partner was currently taking antiretroviral medications (ARVs) and 16.7% reported trying to conceive with their partner (not mutually exclusive). Of women with ARV-using partners, 66.7% reported that their partners were virally suppressed. Retention in PrEP care at three months was 61.1% and, at six months, 37.5%. Further study is necessary to expand PrEP to women whose risk factors extend beyond being in a known sero-discordant partnership, and to understand the reasons for the observed drop-off in PrEP care visits in real-world settings.

Social mixing and correlates of injection frequency among opioid use partnerships

BACKGROUND

As resources are deployed to address the opioid overdose epidemic in the USA, it is essential that we understand the correlates of more frequent opioid injections-which has been associated not only with HIV and HCV transmission, but also with overdose risk-to inform the development and targeting of effective intervention strategies like overdose prevention and naloxone distribution programs. However, no studies have explored how characteristics of opioid use partnerships may be associated within injection frequency with opioid partnerships.

METHODS

Using baseline data from a trial of a behavioural intervention to reduce overdose among opioid users in San Francisco, CA, we calculated assortativity among opioid use partnerships by race, gender, participant-reported HIV- and HCV-status, and opioids used using Newman's assortativity coefficient (NC). Multivariable generalized estimating equations linear regression was used to examine associations between individual- and partnership-level characteristics and injection frequency within opioid use partnerships.

RESULTS

Opioid use partnerships (n=134) reported by study participants (n=55) were assortative by race (NC=0.42, 95%CI=0.33-0.50) and participant-reported HCV-status (NC=0.42, 95%CI=0.31-0.52). In multivariable analyses, there were more monthly injections among sexual/romantic partnerships (β=114.4, 95%CI=60.2-168.7, p<0.001), racially concordant partnerships reported by white study participants (β=71.4, 95%CI=0.3-142.5, p=0.049), racially discordant partnerships reported by African American study participants (β=105.7, 95%CI=1.0-210.5, p=0.048), and partnerships in which either member had witnessed the other experience an overdose (β=81.8, 95%CI=38.9-124.6, p<0.001).

CONCLUSION

Social segregation by race and HCV-status should potentially be considered in efforts to reach networks of opioid users. Due to higher injection frequency and greater likelihood of witnessing their partners experience an overdose, individuals in sexual/romantic opioid use partnerships, white individuals in racially homogenous partnerships, and African American individuals in heterogeneous partnerships may warrant focused attention as part of peer- and network-based overdose prevention efforts, as well as broader HIV/HCV prevention strategies. Developing and targeting overdose prevention education programs that provide information on risk factors and ways to identify overdose, as well as effective responses, including naloxone use and rescue breathing, for more frequently injecting networks may help reduce opioid morbidity and mortality in these most at risk groups.

Theoretical Implications of Gender, Power, and Sexual Scripts for HIV Prevention Programs Aimed at Young, Substance-Using African-American Women

HIV continues to be a major public health problem for African-American (AA) women, and the burden of new cases to our society is significant because each case is at risk of infecting others. Substance use worsens the risk of HIV transmission to AA women. We provide specific recommendations to move the concept of tailoring HIV prevention interventions for substance users forward by focusing on young, sexually active, substance-using AA women and applying a culturally relevant revision to existing theoretical frameworks to include the Sexual Script Theory and the Theory of Gender and Power. We encourage use of these theories to guide adaptation of interventions to demonstrate efficacy within this hard-to-reach population. Consistent use of theories designed to exploit powerlessness and sexual scripts as barriers to adoption of protective sexual behaviors has potential to permeate sexual and substance use networks among African-Americans. This recommendation is being made because this theoretical framework has not been used in HIV prevention interventions targeting young, sexually active, substance-using AA women.

Stigma, sexual risks, and the war on drugs: Examining drug policy and HIV/AIDS inequities among African Americans using the Drug War HIV/AIDS Inequities Model

The relationship between drug policy and HIV vulnerability is well documented. However, little research examines the links between racial/ethnic HIV disparities via the Drug War, sexual risk, and stigma. The Drug War HIV/AIDS Inequities Model has been developed to address this dearth. This model contends that inequitable policing and sentencing promotes sexual risks, resource deprivation, and ultimately greater HIV risk for African-Americans. The Drug War also socially marginalizes African Americans and compounds stigma for incarcerated and formerly incarcerated persons living with HIV/AIDS. This marginalization has implications for sexual risk-taking, access to health-promoting resources, and continuum of care participation. The Drug War HIV/AIDS Inequities Model may help illuminate mechanisms that promote increased HIV vulnerability as well as inform structural intervention development and targeting to address racial/ethnic disparities.

The role of partners' educational attainment in the association between HIV and education amongst women in seven sub-Saharan African countries

INTRODUCTION

Individuals' educational attainment has long been considered as a risk factor for HIV. However, little attention has been paid to the association between partner educational attainment and HIV infection.

METHODS

We conducted cross-sectional analysis of young women (aged 15-34) in 14 Demographic and Health Surveys from seven sub-Saharan Africa (SSA) countries with generalized HIV epidemics. We measured the degree of similarity in educational attainment (partner homophily) in 75,373 partnerships and evaluated the correlation between homophily and female HIV prevalence at the survey cluster level. We then used logistic regression to assess whether own and partner educational attainment was associated with HIV serostatus amongst 38,791 women.

RESULTS

Educational attainment was positively correlated within partnerships in both urban and rural areas of every survey (Newman assortativity coefficients between 0.09 and 0.44), but this correlation was not ecologically associated with HIV prevalence. At the individual level, larger absolute differences between own and partner educational attainment were associated with significantly higher HIV prevalence amongst women. This association was heterogeneous across countries, but not between survey waves. In contrast to other women, for those aged 25-34 who had secondary or higher education, a more-educated partner was associated with lower HIV prevalence.

CONCLUSIONS

HIV prevalence amongst women in SSA is associated not only with one's own education but also with that of one's partner. These findings highlight the importance of understanding how partners place individuals at risk of infection and suggest that HIV prevention efforts may benefit from considering partner characteristics.

Race/Sex Interactions and HIV Testing Among College Students

OBJECTIVES

The primary aim of the study was to examine race/sex interactions and other behavioral and demographic covariates of past-year HIV testing among college students attending a racially diverse historically black university. The relationship between race/sex interactions and engaging with multiple sex partners during the past year was also examined.

PARTICIPANTS

The sample included 566 students who identified as Black or White and engaged in vaginal, oral, or anal sex during the past 12 months.

METHODS

A total of 113 undergraduate classes were randomly selected, stratified by time of day. Surveys were administered by project team members who were assisted by peer health educators to increase the cultural competency of the study. The response rate was 94 %.

RESULTS

The sample of 566 participants included Black women (54 %), Black men (26 %), White women (13 %), and White men (7 %). The mean age was 25 (median = 22 years), and 42 % resided on campus. Nearly half (46 %) reported two or more sex partners in the past year, and 9 % of participants were diagnosed with STD in the past year. Sixty-nine percent reported being tested for HIV, 58 % had been tested in the past year, and 18 % had been tested for HIV on two or more occasions during the past year. In multivariable analysis, Black men (AOR = 0.43; 95 % CI = 0.27, 0.69), White women (AOR = 0.25; 95 % CI = 0.14, 0.47), and White men (AOR = 0.22; 95 % CI = 0.10, 0.49) were significantly less likely than Black women to be tested for HIV in the past year. Residing off campus (AOR = 1.88; 95 % CI = 1.18, 2.99) and engaging with two or more sex partners in the past year (AOR = 2.59; 95 % CI = 1.70, 3.95) significantly increased the likelihood of HIV testing in the past year. Students who engaged only with heterosexual partners (AOR = .25; 95 % CI = 0.09, 0.76) or were female and bisexual (AOR = 0.17; 95 % CI = 0.04, 0.69) were less likely to be tested for HIV in the past year compared to men who have sex with men/men and women. In a separate model, Black men (AOR = 1.87; 95 % CI = 1.18, 2.97) were significantly more likely than Black women to engage with two or more sex partners during the previous year. Compared to Black women, White women (AOR = 0.51; 95 % CI = 0.26, 0.98) were less likely to report two or more sex partners in the past year. Students involved in a relationship during the past 30 days (AOR = 0.33; 95 % CI = 0.22, 0.49) were less likely than other students to engage with two or more sex partners in the past year.

CONCLUSIONS

Over half (58 %) of the students had been tested for HIV in the past year-a promising outcome. However, 42 % of sexually active students had not been tested. Campus prevention initiatives need to reinforce the importance of frequent HIV testing. In particular, targeted prevention efforts need to be focused on heterosexual Black male college students.

Gang membership and marijuana use among African American female adolescents in North Carolina

The southeastern US sustains the highest high school dropout rates, and gangs persist in underserved communities. African American female adolescents who drop out of school and are gang members are at substantial risk of exposure to severe violence, physical abuse, and sexual exploitation. In this study of 237 female African American adolescents 16-19 years of age from North Carolina who dropped out or considered dropping out, 11% were current or past gang members. Adolescents who reported gang membership began smoking marijuana at a mean age of 13, whereas those who reported no gang membership began at a mean age of 15 years (P<0.001). The mean ages of first alcohol use were 14 years and 15 years for gang members and non-gang members, respectively (P=0.04). Problem alcohol use was high in both groups: 40% and 65% for non-gang and gang members, respectively (P=0.02). Controlling for frequent marijuana use and problem alcohol use, adolescents who reported gang membership were more likely than non-gang members to experience sexual abuse (odds ratio [OR] =2.60, 95% confidence interval [CI] [1.06, 6.40]), experience physical abuse (OR =7.33, 95% CI [2.90, 18.5]), report emotional abuse from their main partner (OR =3.55, 95% CI [1.44, 8.72]), run away from home (OR =4.65, 95% CI [1.90, 11.4]), get arrested (OR =2.61, 95% CI [1.05, 6.47]), and report violence in their neighborhood including murder (OR =3.27, 95% CI [1.35, 7.96]) and fights with weapons (OR =3.06, 95% CI [1.15, 8.11]). Gang members were less likely to receive emotional support (OR =0.89, 95% CI [0.81, 0.97]). These findings reinforce the urgent need to reach young African American women in disadvantaged communities affiliated with gangs to address the complexity of context and interconnected risk behaviors.

It is complicated: sexual partner characteristic profiles and sexually transmitted infection rates within a predominantly African American population in Mississippi

BACKGROUND

Mississippi has among the highest prevalence of sexually transmitted infections (STIs) in the United States. Understanding sexual networks can provide insight into risk factors for transmission and guide prevention interventions.

METHODS

Participants included 1437 primarily African American (95%) adults presenting for care at an STI clinic in Jackson, Mississippi. Latent class analysis identified underlying population subgroups with unique patterns of response on a comprehensive set of 14 sexual partner variables, such as living with or having a child with a partner, partner dependence and trust, 1-time sexual encounters, multiple main partners, substance use, sexual concurrency, and incarceration. Classes were compared on participant age, sex, sexual orientation, public assistance, lifetime partners, relationship status, and self-reported past-year STI.

RESULTS

Three classes emerged. Class 1 (n = 746) participants were less dependent on partners and less likely to live with or have a child with a partner. Class 2 participants (n = 427) endorsed multiple STI risk factors, including partner incarceration, 6 or more lifetime partners, sexual concurrency, 1-time sexual encounters, and substance use at last sex. Class 3 participants (n = 226) were more likely to be in dependent, committed relationships with children. Class 2 had a higher proportion of self-report past-year STIs (36.7%) compared with classes 1 (26.6%) and 3 (26.1%).

CONCLUSIONS

Certain partner factors such as incarceration, substance use, and concurrency may contribute to increased STI risk. Partner factors may be useful proxies for STI risks and could be useful questions to include in screening questionnaires in clinical settings.

"Condoms are the standard, right?": Exploratory study of the reasons for using condoms by Black American emerging adult women

Condoms are considered a highly effective form of sexually transmitted infection prevention for heterosexual sex. Black American women (BAW) have been and are at elevated risk for heterosexual exposure to human immunodeficiency virus (HIV) because they have been and continue to be less likely to negotiate condom use with a partner that supports them financially. However, BAW who have made tremendous educational gains may still encounter challenges regarding the distribution of power that can affect condom use and negotiation. The purpose of this exploratory study was to examine the reasons that highly educated, emerging, adult BAW reported for using condoms. One hundred twenty-seven emerging adult BAW (ages 18-29 years) completed a mixed-methods online survey during the spring of 2013 (January-May). Approximately 80% of the women were in college or college graduates. They had a high rate of previous HIV testing (68.5%). Through the use of an interpretive paradigm and grounded theory, three themes emerged regarding the reasons that the participants in this sample used condoms as their primary form of protection: (1) the reliable "standard," (2) pregnancy prevention, and (3) cost effective and "easily accessible." Findings are discussed in terms of their public health significance for this seemingly lower-risk population.

Disassortative mixing patterns of drug-using and sex networks on HIV risk behaviour among young drug users in Yunnan, China

OBJECTIVES

The dominant mode of HIV transmission in China has changed from injection drug use to sexual contact. The objectives of this study were to describe the disassortative and assortative mixing patterns of drug-using and sex networks among young drug users in China.

STUDY DESIGN

Cross-sectional study.

METHODS

Respondent-driven sampling (RDS) was used to recruit young drug users in an egocentric network study in Yunnan, China. Egos were categorized as having disassortative mixing network patterns if they reported both sex and drug-using networks. Egos who only had a sex network (no drug-using network), or only a drug-using network (no sex network) were categorized as having assortative mixing network patterns. Multiple logistic regression was performed to analyze the relationships between disassortative patterns with risky sexual behaviour and drug-using practices.

RESULTS

A total of 426 participants were recruited into the study. Two hundred forty-two egos reported disassortative mixing patterns and 139 egos had assortative patterns. The RDS-adjusted proportion of having a disassortative pattern was 53.2%. Participants with disassortative patterns were more likely to engage in HIV risk behaviour compared to those with assortative patterns. Specifically, drug users with disassortative patterns reported more multiple sex partners (31.4% vs 19.6%), concurrent partnerships (52.1% vs 39.0%), non-regular sex partners (12.0% vs 4.3%), and sex partners who were IDUs (24.9% vs 12.5%). Consistent condom use with regular or non-regular partners was low (between 18.9% and 47.2%) regardless of the mixing pattern. However, parenteral risk for HIV transmission was relatively low in both groups.

CONCLUSIONS

The transition of the HIV epidemic in China from injection drug use to sexual contact may be attributed to disassortative mixing in drug-use and sexual networks. HIV programs should consider disassortative mixing patterns when designing new behavioural interventions.

Sexual Networks and HIV Risk among Black Men Who Have Sex with Men in 6 U.S. Cities

BACKGROUND

Sexual networks may place U.S. Black men who have sex with men (MSM) at increased HIV risk.

METHODS

Self-reported egocentric sexual network data from the prior six months were collected from 1,349 community-recruited Black MSM in HPTN 061, a multi-component HIV prevention intervention feasibility study. Sexual network composition, size, and density (extent to which members are having sex with one another) were compared by self-reported HIV serostatus and age of the men. GEE models assessed network and other factors associated with having a Black sex partner, having a partner with at least two age category difference (age difference between participant and partner of at least two age group categories), and having serodiscordant/serostatus unknown unprotected anal/vaginal intercourse (SDUI) in the last six months.

RESULTS

Over half had exclusively Black partners in the last six months, 46% had a partner of at least two age category difference, 87% had ≤5 partners. Nearly 90% had sex partners who were also part of their social networks. Among HIV-negative men, not having anonymous/exchange/ trade partners and lower density were associated with having a Black partner; larger sexual network size and having non-primary partners were associated with having a partner with at least two age category difference; and having anonymous/exchange/ trade partners was associated with SDUI. Among HIV-positive men, not having non-primary partners was associated with having a Black partner; no sexual network characteristics were associated with having a partner with at least two age category difference and SDUI.

CONCLUSIONS

Black MSM sexual networks were relatively small and often overlapped with the social networks. Sexual risk was associated with having non-primary partners and larger network size. Network interventions that engage the social networks of Black MSM, such as interventions utilizing peer influence, should be developed to address stable partnerships, number of partners, and serostatus disclosure.

Correlates of Concurrent Sexual Partnerships Among Young, Rural African American Men

OBJECTIVE

We investigated the social, behavioral, and psychological factors associated with concurrent (i.e., overlapping in time) sexual partnerships among rural African American young men with a primary female partner.

METHODS

We recruited 505 men in rural areas of southern Georgia from January 2012 to August 2013 using respondent-driven sampling; 361 reported having a primary female partner and participating only in heterosexual sexual activity. Men provided data on their demographic characteristics and HIV-related risk behaviors, as well as social, behavioral, and psychological risk factors.

RESULTS

Of the 361 men with a primary female partner, 164 (45.4%) reported concurrent sexual partners during the past three months. Among the 164 men with a concurrent sexual partner, 144 (92.9%) reported inconsistent condom use with their primary partners, and 68 (41.5%) reported using condoms inconsistently with their concurrent partners. Having concurrent sexual partnerships was associated with inconsistent condom use, substance use before sex, and self-reported sexually transmitted infections (STIs). Bivariate correlates of concurrent sexual partnerships included incarceration, substance use, early onset of sexual activity, impulsive decision-making, and masculinity attitudes (i.e., men's adherence to culturally defined standards for male behavior). In a multivariate model, both masculinity ideology and impulsive decision-making independently predicted concurrent sexual partnerships independent of other risk factors.

CONCLUSION

Masculinity attitudes and impulsive decision-making are independent predictors of concurrent sexual partnerships among rural African American men and, consequently, the spread of HIV and other STIs. Developing programs that target masculinity attitudes and self-regulatory skills may help to reduce concurrent sexual partnerships.

Sexual Behaviors of US Women at Risk of HIV Acquisition: A Longitudinal Analysis of Findings from HPTN 064

We describe the sexual behaviors of women at elevated risk of HIV acquisition who reside in areas of high HIV prevalence and poverty in the US. Participants in HPTN 064, a prospective HIV incidence study, provided information about individual sexual behaviors and male sexual partners in the past 6 months at baseline, 6- and 12-months. Independent predictors of consistent or increased temporal patterns for three high-risk sexual behaviors were assessed separately: exchange sex, unprotected anal intercourse (UAI) and concurrent partnerships. The baseline prevalence of each behavior was >30 % among the 2,099 participants, 88 % reported partner(s) with >1 HIV risk characteristic and both individual and partner risk characteristics decreased over time. Less than high school education and food insecurity predicted consistent/increased engagement in exchange sex and UAI, and partner's concurrency predicted participant concurrency. Our results demonstrate how interpersonal and social factors may influence sustained high-risk behavior by individuals and suggest that further study of the economic issues related to HIV risk could inform future prevention interventions.

Changes in Exposure to Neighborhood Characteristics are Associated with Sexual Network Characteristics in a Cohort of Adults Relocating from Public Housing

Ecologic and cross-sectional multilevel analyses suggest that characteristics of the places where people live influence their vulnerability to HIV and other sexually-transmitted infections (STIs). Using data from a predominately substance-misusing cohort of African-American adults relocating from US public housing complexes, this multilevel longitudinal study tested the hypothesis that participants who experienced greater post-relocation improvements in economic disadvantage, violent crime, and male:female sex ratios would experience greater reductions in perceived partner risk and in the odds of having a partner who had another partner (i.e., indirect concurrency). Baseline data were collected from 172 public housing residents before relocations occurred; three waves of post-relocation data were collected every 9 months. Participants who experienced greater improvements in community violence and in economic conditions experienced greater reductions in partner risk. Reduced community violence was associated with reduced indirect concurrency. Structural interventions that decrease exposure to violence and economic disadvantage may reduce vulnerability to HIV/STIs.

Racial/Ethnic Differences in Sexual Network Mixing: A Log-Linear Analysis of HIV Status by Partnership and Sexual Behavior Among Most at-Risk MSM

Mixing patterns within sexual networks have been shown to have an effect on HIV transmission, both within and across groups. This study examined sexual mixing patterns involving HIV-unknown status and risky sexual behavior conditioned on assortative/dissortative mixing by race/ethnicity. The sample used for this study consisted of drug-using male sex workers and their male sex partners. A log-linear analysis of 257 most at-risk MSM and 3,072 sex partners was conducted. The analysis found two significant patterns. HIV-positive most at-risk Black MSM had a strong tendency to have HIV-unknown Black partners (relative risk, RR = 2.91, p < 0.001) and to engage in risky sexual behavior (RR = 2.22, p < 0.001). White most at-risk MSM with unknown HIV status also had a tendency to engage in risky sexual behavior with Whites (RR = 1.72, p < 0.001). The results suggest that interventions that target the most at-risk MSM and their sex partners should account for specific sexual network mixing patterns by HIV status.

[Sexually transmitted diseases: the impact of stigma and taboo on current medical care]

Sexually transmitted diseases (STD) are probably the most tabooed diseases we know. The many taboos and the related stigmata shape patients' lives and significantly influence health care policies, medical research, and current problems in medical ethics. To better understand these complex influences, the still powerful taboos and related metaphors associated with illness and disease are analyzed within their cultural and historical background and concerning the actual impact on patient care and research. It becomes obvious that research and health care policies cannot be satisfyingly successful in helping people affected by STDs as long as these "nonscientific" factors are not taken into account.

Knowing is not enough: a qualitative report on HIV testing among heterosexual African-American men

Despite having higher rates of HIV testing than all other racial groups, African-Americans continue to be disproportionately affected by the HIV epidemic in the United States. Knowing one's status is the key step to maintaining behavioral changes that could stop the spread of the virus, yet little is known about the individual- and socio-structural-level barriers associated with HIV testing and communication among heterosexual African-American men. To address this and inform the development of an HIV prevention behavioral intervention for heterosexual African-American men, we conducted computerized, structured interviews with 61 men, focus group interviews with 25 men in 5 different groups, and in-depth qualitative interviews with 30 men living in high HIV prevalence neighborhoods in New York City. Results revealed that HIV testing was frequent among the participants. Even with high rates of testing, the men in the study had low levels of HIV knowledge; perceived little risk of HIV; and misused HIV testing as a prevention method. Factors affecting HIV testing, included stigma, relationship dynamics and communication, and societal influences, suggesting that fear, low perception of risk, and HIV stigma may be the biggest barriers to HIV testing. These results also suggest that interventions directed toward African-American heterosexual men must address the use of "testing as prevention" as well as correct misunderstandings of the window period and the meaning of HIV test results, and interventions should focus on communicating about HIV.

Patterns of sexual mixing with respect to social, health and sexual characteristics among heterosexual couples in England: analyses of probability sample survey data

Patterns of sexual mixing are major determinants of sexually transmitted infection (STI) transmission, in particular the extent to which high-risk populations mix with low-risk populations. However, patterns of mixing in the general population are poorly understood. We analysed data from a national probability sample survey of households, the Health Survey for England 2010. A total of 943 heterosexual couples living together, where at least one partner was aged between 16–44 years, were included. We used correlation coefficients to measure the strength of similarities between partners with respect to demographic characteristics, general health, health behaviours and sexual history. Males were on average 2 years older than their female partners, although this age difference ranged from a median of 0 years in men aged 16–24 years to a median of 2 years in men aged 35–44 years. A positive correlation between partners was found for all demographic characteristics. With respect to general health and health behaviours, a strongly positive correlation was found between men and women in reporting alcohol consumption at ⩾3 days a week and smoking. Men typically reported greater numbers of sexual partners than their female partner, although men and women with more partners were more likely to mix with each other. We have been able to elucidate the patterns of sexual mixing between men and women living together in England. Mixing based on demographic characteristics was more assortative than sexual characteristics. These data can better inform mathematical models of STI transmission.

Sexual mixing and the risk environment of sexually active transgender women: data from a respondent-driven sampling study of HIV risk among transwomen in San Francisco, 2010

Background

Research on the sexual networks of transwomen is central to explaining higher HIV risk for this population. This study examined HIV risk behaviors and sexual mixing patterns of transwomen by demographic and HIV-related risk behaviors.

Methods

Data were obtained from a 2010 study of HIV risk for transwomen in San Francisco. Assortativity by race, partner type, HIV serostatus, and IDU across sexual networks was calculated using Newman’s assortativity coefficient (NC). Multivariable generalized estimating equations (GEE) logistic regression models were used to evaluate associations between unprotected anal intercourse with race and HIV serostatus, partner-IDU status and relationship type discordance while adjusting for the HIV status of transwomen.

Results

There were 235 sexually active transwomen in this study, of whom 104 (44.3%) were HIV-positive and 73 (31.1%) had a history of injection drug use. Within the 575 partnerships, African American/black and Latina transwomen were the most racially assortative (NC 0.40, 95% CI 0.34-0.45, and NC 0.43, 95% CI 0.38-0.49, respectively). In partnerships where the partner’s HIV status was known (n = 309, 53.7%), most transwomen were in sexual partnerships with people of their same known serostatus (71.8%, n = 222). In multivariable analyses, unprotected anal intercourse was significantly associated with primary partners, having a sexual partner who was an injection drug user, and sexual partner seroconcordance.

Conclusions

Public health efforts to reduce transwomen’s HIV risk would likely benefit from prioritizing prevention efforts to risk reduction within IDU-discordant and primary partnerships, determining risks attributable to sexual network characteristics, and actively addressing injection drug use among transwomen.

Development, calibration and performance of an HIV transmission model incorporating natural history and behavioral patterns: application in South Africa

Understanding HIV transmission dynamics is critical to estimating the potential population-wide impact of HIV prevention and treatment interventions. We developed an individual-based simulation model of the heterosexual HIV epidemic in South Africa and linked it to the previously published Cost-Effectiveness of Preventing AIDS Complications (CEPAC) International Model, which simulates the natural history and treatment of HIV. In this new model, the CEPAC Dynamic Model (CDM), the probability of HIV transmission per sexual encounter between short-term, long-term and commercial sex worker partners depends upon the HIV RNA and disease stage of the infected partner, condom use, and the circumcision status of the uninfected male partner. We included behavioral, demographic and biological values in the CDM and calibrated to HIV prevalence in South Africa pre-antiretroviral therapy. Using a multi-step fitting procedure based on Bayesian melding methodology, we performed 264,225 simulations of the HIV epidemic in South Africa and identified 3,750 parameter sets that created an epidemic and had behavioral characteristics representative of a South African population pre-ART. Of these parameter sets, 564 contributed 90% of the likelihood weight to the fit, and closely reproduced the UNAIDS HIV prevalence curve in South Africa from 1990–2002. The calibration was sensitive to changes in the rate of formation of short-duration partnerships and to the partnership acquisition rate among high-risk individuals, both of which impacted concurrency. Runs that closely fit to historical HIV prevalence reflect diverse ranges for individual parameter values and predict a wide range of possible steady-state prevalence in the absence of interventions, illustrating the value of the calibration procedure and utility of the model for evaluating interventions. This model, which includes detailed behavioral patterns and HIV natural history, closely fits HIV prevalence estimates.

Who mixes with whom among men who have sex with men? Implications for modelling the HIV epidemic in southern India

In India, the identity of men who have sex with men (MSM) is closely related to the role taken in anal sex (insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role segregation (taking only the insertive or receptive role) and the extent of assortative (within-group) mixing are known to affect HIV epidemic size in other settings and populations. This study explores how different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India, affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to disassortative (minimising within-group mixing). A simple model was used to obtain insights into the relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore. With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were seen between the fits identified using different mixing scenarios, but little difference was projected in future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled, targeted at the different identity groups. For intervention strategies targeting the receptive or receptive and versatile MSM together, the overall impact was very similar for different mixing patterns. However, for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for different mixing scenarios; more impact was achieved with greater levels of disassortative mixing.

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Different mixing scenarios are explored for 3 groups of role-segregated MSM.

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Models show that the mixing scenario affects both R₀ and endemic HIV prevalence.

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When models are fit to data, predicted HIV trends are unaffected by mixing.

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Impact of targeted (but not non-targeted) interventions can be affected by mixing.

Assortativity coefficient-based estimation of population patterns of sexual mixing when cluster size is informative

OBJECTIVES

Population sexual mixing patterns can be quantified using Newman's assortativity coefficient (r). Suggested methods for estimating the SE for r may lead to inappropriate statistical conclusions in situations where intracluster correlation is ignored and/or when cluster size is predictive of the response. We describe a computer-intensive, but highly accessible, within-cluster resampling approach for providing a valid large-sample estimated SE for r and an associated 95% CI.

METHODS

We introduce needed statistical notation and describe the within-cluster resampling approach. Sexual network data and a simulation study were employed to compare within-cluster resampling with standard methods when cluster size is informative.

RESULTS

For the analysis of network data when cluster size is informative, the simulation study demonstrates that within-cluster resampling produces valid statistical inferences about Newman's assortativity coefficient, a popular statistic used to quantify the strength of mixing patterns. In contrast, commonly used methods are biased with attendant extremely poor CI coverage. Within-cluster resampling is recommended when cluster size is informative and/or when there is within-cluster response correlation.

CONCLUSIONS

Within-cluster resampling is recommended for providing valid statistical inferences when applying Newman's assortativity coefficient r to network data.