Racial and Ethnic Differences in Mobile App Use for Meeting Sexual Partners Among Young Men Who Have Sex With Men and Young Transgender Women: Cross-Sectional Study.

Background: Young men who have sex with men and young transgender women (YMSM-YTW) use online spaces to meet sexual partners with increasing regularity, and research shows that experiences of racism online mimics the real world. Objective: We analyzed differences by race and ethnicity in web-based and mobile apps used to meet sexual partners as reported by Chicago-based YMSM-YTW in 2016-2017. Methods: A racially and ethnically diverse sample of 643 YMSM-YTW aged 16-29 years were asked to name websites or mobile apps used to seek a sexual partner in the prior 6 months, as well as provide information about sexual partnerships from the same period. We used logistic regression to assess the adjusted association of race and ethnicity with (1) use of any website or mobile apps to find a sexual partner, (2) use of a "social network" to find a sexual partner compared to websites or mobile apps predominantly used for dating or hookups, (3) use of specific websites or mobile apps, and (4) reporting successfully meeting a sexual partner online among website or mobile app users. Results: While most YMSM-YTW (454/643, 70.6%) used websites or mobile apps to find sexual partners, we found that Black non-Hispanic YMSM-YTW were significantly less likely to report doing so (comparing White non-Hispanic to Black non-Hispanic: adjusted odds ratio [aOR] 1.74, 95% CI 1.10-2.76). Black non-Hispanic YMSM-YTW were more likely to have used a social network site to find a sexual partner (comparing White non-Hispanic to Black non-Hispanic: aOR 0.20, 95% CI 0.11-0.37), though this was only reported by one-third (149/454, 32.8%) of all app-using participants. Individual apps used varied by race and ethnicity, with Grindr, Tinder, and Scruff being more common among White non-Hispanic YMSM-YTW (93/123, 75.6%; 72/123, 58.5%; and 30/123, 24.4%, respectively) than among Black non-Hispanic YMSM-YTW (65/178, 36.5%; 25/178, 14%; and 4/178, 2.2%, respectively) and Jack'd and Facebook being more common among Black non-Hispanic YMSM-YTW (105/178, 59% and 64/178, 36%, respectively) than among White non-Hispanic YMSM-YTW (6/123, 4.9% and 8/123, 6.5%, respectively). Finally, we found that while half (230/454, 50.7%) of YMSM-YTW app users reported successfully meeting a new sexual partner on an app, Black non-Hispanic YMSM-YTW app users were less likely to have done so than White non-Hispanic app users (comparing White non-Hispanic to Black non-Hispanic: aOR 2.46, 95% CI 1.50-4.05). Conclusions: We found that Black non-Hispanic YMSM-YTW engaged with websites or mobile apps and found sexual partners systematically differently than White non-Hispanic YMSM-YTW. Our findings give a deeper understanding of how racial and ethnic sexual mixing patterns arise and have implications for the spread of sexually transmitted infections among Chicago's YMSM-YTW.

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.

HPV vaccination and sexual behaviour in healthcare seeking young women in Luxembourg.

INTRODUCTION: Human papillomavirus (HPV) is the most common sexually transmitted infection (STI) worldwide. Despite recommendations for HPV vaccination of young women from health authorities, parental concerns were raised whether vaccination could induce unsafe sexual behaviour in young women. Therefore, the primary aim of this study was to investigate if HPV vaccination in healthcare seeking adult women in Luxembourg was associated with unsafe sexual behaviour. METHODS: Seven hundred twenty-nine women (mean age = 22.5; range 18-43 years) were recruited either at Luxembourg family planning centres or at private gynaecology practices. All participants completed a questionnaire on vaccination status and sexual behaviour. Poisson and logistic regressions were used to study the association between sexual behaviour and vaccination status (N = 538). Both models were restricted to women younger than 26 years, since the first cohort being vaccinated would be 25 years old at the time of sampling. Assortativity of sexual mixing by age was also assessed for further transmission modelling for women <30 years reporting age of last/current sexual partner (N = 649). Women older than 29 years were excluded from the assortativity analysis due to restricted sample size. RESULTS: In total, 386/538 (71.8%) of participants reported receiving HPV vaccine. Vaccination uptake significantly varied by nationality and was higher in Portuguese 112/142 (78.9%) and in Luxembourgish 224/313(71.6%) residents, and lower in residents of other nationalities 50/83 (60.2%) (p = 0.011). HPV vaccination was not associated with unsafe sexual behaviour such as shorter relationship duration with current or last sexual partner (odds ratio (OR) = 1.05, 95% CI [0.94-1.16]), younger age of sexual debut (OR = 1.00, 95% CI [0.88-1.14]), increased number of lifetime sexual partners (OR = 0.95, 95% CI [0.87-1.03), higher age difference with sexual partner (OR = 1.01, 95% CI [0.95-1.08]), condom use (OR = 0.97, 95% CI [0.60-1.56]), nor with other factors like smoking (OR = 0.73, 95% CI [0.47-1.15]) and nationality. HPV vaccination was only associated with younger age (OR = 0.84, 95% CI [0.75-0.94]). Relationship duration, age of sexual debut, age difference with sexual partner, smoking, age and non-Portuguese foreign nationality were predictors of number of lifetime sexual partners. Assortativity analysis revealed that young women chose sexual partners who were 2.3 years older on average. CONCLUSIONS: Our study found no association between unsafe sexual behaviour and HPV vaccination.

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.

The Social Geography of Partner Selection in Toronto, Canada: A Qualitative Description of "Convection Mixing".

The geographic distribution of sexually transmitted infections reflects the underlying social process of sexual partner selection. This qualitative study explored the social geography of partner selection among sexual minority men and used the results to develop a mid-range theory of STI transmission. In-depth interviews with 31 sexual minority men who lived, worked, or socialized in Toronto, Canada, occurred in June and July 2016. Participants were asked how they found sexual partners and reconstructed their egocentric sexual networks for the previous 3 months. Participants described an iterative process of partner selection involving intention (sex versus dating), connecting with community, and selecting a partner based on intersecting partner characteristics (external, internal, and emergent feelings when interacting with potential partners) and personal preferences. Geography influenced partner selection three ways: (1) participant search patterns maximized the number of potential partners in the shortest distance possible; (2) the density of sexual minority men in a participant's community directly impacted participant's social and sexual isolations; and (3) geosexual isolation influenced sexual mixing patterns. Participants described "convection mixing," where assortative urban mixing nested within disassortative suburban mixing resulted in movement from the suburbs to downtown and back to the suburbs. We theorize that convection mixing may be contributing to the persistence of STI epidemics in core and outbreak areas by creating STI reservoirs outside of, and connected to, core and outbreak areas.

Population-Level Sexual Mixing According to HIV Status and Preexposure Prophylaxis Use Among Men Who Have Sex With Men in Montreal, Canada: Implications for HIV Prevention.

Using cross-sectional survey data (Engage, 2017-2018) from 1,137 men who have sex with men, ≥16 years old, in Montreal, we compared observed human immunodeficiency virus (HIV) seroconcordance in previous-6-months' sexual partnerships with what would have been observed by chance if zero individuals serosorted. Of 5 recent partnerships where both individuals were HIV-negative, we compared observed concordance in preexposure prophylaxis (PrEP) use with the counterfactual if zero individuals selected partners based on PrEP use. We estimated the concordance by chance using a balancing-partnerships approach assuming proportionate mixing. HIV-positive respondents had a higher proportion of HIV-positive partners (66.4%, 95% confidence interval (CI): 64.0, 68.6) than by chance (23.9%, 95% CI: 23.1, 24.7). HIV-negative respondents (both on and not on PrEP) had higher proportions of HIV-negative partners (82.9% (95% CI: 81.1, 84.7) and 90.7% (95% CI: 89.6, 91.7), respectively) compared with by chance (76.1%, 95% CI: 75.3, 76.9); however, those on PrEP had a higher proportion of HIV-positive partners than those not on PrEP (17.1% (95% CI: 15.3, 18.9) vs. 9.3% (95% CI: 8.3, 10.4). Those on PrEP also had a higher proportion of partners on PrEP among their HIV-negative partners (50.6%, 95% CI: 42.5, 58.8) than by chance (28.5%, 95% CI: 27.5, 29.4). The relationship between PrEP and sexual-mixing patterns demonstrated by less population-level serosorting among those on PrEP and PrEP-matching warrants consideration during PrEP roll-out.

Sexual mixing in opposite-sex partnerships in Britain and its implications for STI risk: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3).

BACKGROUND: The extent to which individuals are similar to their sexual partners influences STI-transmission probabilities, yet there is a dearth of empirical data, especially those representative of the population. METHODS: Analyses of data reported by 10 759 sexually active people aged 16-74 y interviewed for a British national probability survey undertaken in 2010-12. Computer-assisted self-interviews asked about partner numbers and characteristics of participants' three most recent partnerships (MRPs). Opposite-sex MRPs were weighted to represent all such partnerships in the past year (N = 16 451). Estimates of disassortative age mixing (≥±5-y difference), ethnic mixing (partner of a different ethnic group) and geographical mixing (partner from a different region/country when they first met) were calculated, stratified by gender, age group and partnership status (casual/steady). Multivariable regression examined how these disassortative mixing measures were associated with STI-risk measures: condom use at first sex together at the partnership-level and, at the participant-level, STI-risk perception and reporting STI diagnoses. RESULTS: Disassortative age mixing occurred in around one-third of opposite-sex partnerships, with men ≥5 y older in most cases, although this proportion varied by participant's gender and age group. Ethnic mixing occurred less frequently (11.3% of men's and 8.6% of women's partnerships) as did geographical mixing (14.1 and 16.3%, respectively). Disassortative mixing was more common among casual vs steady partnerships. Condom use at first sex was less likely in women's partnerships that were age-disassortative [adjusted odds ratio (AOR): 0.79, 95% confidence interval (CI): 0.69-0.95], whereas men reporting disassortative ethnic mixing were more likely to perceive themselves at STI risk (AOR: 1.76, 95% CI: 1.23-2.52) and report STI diagnoses (AOR: 2.37, 95% CI: 1.22-4.59). CONCLUSIONS: Disassortative mixing, although uncommon among opposite-sex partnerships in Britain, is independently associated with STI risk, warranting consideration in STI-prevention efforts.

Revisiting assumptions about age-based mixing representations in mathematical models of sexually transmitted infections.

BACKGROUND: Sexual mixing between heterogeneous population subgroups is an integral component of mathematical models of sexually transmitted infections (STIs). This study compares the fit of different mixing representations to survey data and the impact of different mixing assumptions on the predicted benefits of hypothetical human papillomavirus (HPV) vaccine strategies. METHODS: We compared novel empirical (data-driven) age mixing structures with the more commonly-used assortative-proportionate (A-P) mixing structure. The A-P mixing structure assumes that a proportion of sexual contacts - known as the assortativity constant, typically estimated from survey data or calibrated - occur exclusively within one's own age group and the remainder mixes proportionately among all age groups. The empirical age mixing structure was estimated from the National Survey on Sexual Attitudes and Lifestyles 3 (Natsal-3) using regression methods, and the assortativity constant was estimated from Natsal-3 as well. Using a simplified HPV transmission model under each mixing assumption, we calibrated the model to British HPV16 prevalence data, then estimated the reduction in steady-state prevalence and the number of infections averted due to expanding HPV vaccination from 12- through 26-year-old females alone to 12-year-old males or 27- to 39-year-old females. RESULTS: Empirical mixing provided a better fit to the Natsal-3 data than the best-fitting A-P structure. Using the model with empirical mixing as a reference, the model using the A-P structure often under- or over-estimated the benefits of vaccination, in one case overestimating by 2-fold the number of infections prevented due to extended female catch-up in a high vaccine uptake setting. CONCLUSIONS: An empirical mixing structure more accurately represents sexual mixing survey data, and using the less accurate, yet commonly-used A-P structure has a notable effect on estimates of HPV vaccination benefits. This underscores the need for mixing structures that are less dependent on unverified assumptions and are directly informed by sexual behavior data.

Simultaneously characterizing the comparative economics of routine female adolescent nonavalent human papillomavirus (HPV) vaccination and assortativity of sexual mixing in Hong Kong Chinese: a modeling analysis.

BACKGROUND: Although routine vaccination of females before sexual debut against human papillomavirus (HPV) has been found to be cost-effective around the world, its cost-benefit has rarely been examined. We evaluate both the cost-effectiveness and cost-benefit of routine female adolescent nonavalent HPV vaccination in Hong Kong to guide its policy, and by extension that of mainland China, on HPV vaccination. One major obstacle is the lack of data on assortativity of sexual mixing. Such difficulty could be overcome by inferring sexual mixing parameters from HPV epidemiologic data. METHODS: We use an age-structured transmission model coupled with stochastic individual-based simulations to estimate the health and economic impact of routine nonavalent HPV vaccination for girls at age 12 on cervical cancer burden and consider vaccine uptake at 25%, 50%, and 75% with at least 20 years of vaccine protection. Bayesian inference was employed to parameterize the model using local data on HPV prevalence and cervical cancer incidence. We use the human capital approach in the cost-benefit analysis (CBA) and GDP per capita as the indicative willingness-to-pay threshold in the cost-effectiveness analysis (CEA). Finally, we estimate the threshold vaccine cost (TVC), which is the maximum cost for fully vaccinating one girl at which routine female adolescent nonavalent HPV vaccination is cost-beneficial or cost-effective. RESULTS: As vaccine uptake increased, TVC decreased (i.e., economically more stringent) in the CBA but increased in the CEA. When vaccine uptake was 75% and the vaccine provided only 20 years of protection, the TVC was US$444 ($373-506) and $689 ($646-734) in the CBA and CEA, respectively, increasing by approximately 2-4% if vaccine protection was assumed lifelong. TVC is likely to be far higher when non-cervical diseases are included. The inferred sexual mixing parameters suggest that sexual mixing in Hong Kong is highly assortative by both age and sexual activity level. CONCLUSIONS: Routine HPV vaccination of 12-year-old females is highly likely to be cost-beneficial and cost-effective in Hong Kong. Inference of sexual mixing parameters from epidemiologic data of prevalent sexually transmitted diseases (i.e., HPV, chlamydia, etc.) is a potentially fruitful but largely untapped methodology for understanding sexual behaviors in the population.

San Franciscan MSM have similar types and numbers of partnerships with men inside San Francisco and outside San Francisco, 2011.

Sexual networks among men who have sex with men (MSM) across health jurisdictions may play a role in HIV transmission and acquisition. Levels of HIV prevention activities may be different across health jurisdictions leading to differential risk for HIV transmission with partners in and outside of San Francisco (SF). We examined MSM sexual partnerships within and outside SF. Data were collected during the 2011 National HIV Behavioral Surveillance MSM data collection cycle. Participants were asked to report characteristics of and sexual behaviors with up to five most recent sexual partners. Restricting our analysis to sexually active San Franciscans (n = 329 MSM reporting 927 partnerships), we found that SF MSM have similar numbers of partnerships (SF mean = 1.3, non-SF mean = 1.2) and levels of risk behavior with men within and outside SF. With the current intensity of HIV prevention occurring in SF additional strategies may be needed to address the fact that SF MSM have many sexual connections to men in other health jurisdictions where HIV prevention may not be similar to those in SF.

Sexual partner mixing and differentials in consistent condom use among men who have sex with men in Maharashtra, India.

Sexual partner mixing among men who have sex with men (MSM), based on both gender and partnership status, is an understudied theme in India. Using data from Round 2 of the Integrated Bio-behavioral Survey, this paper reports on gender and partnership status-based sexual mixing and levels of consistent condom use (CCU) among MSM in Maharashtra. A total of 689 MSM were sampled using probability-based sampling. Bivariate and regression analyses were carried out on condom use and partnership mixing. Over half (52%) of all MSM reported having only male partners while about one-third (34.5%) reported having partners of both gender. Over 70% of MSM engaged in sex with a mix of casual, regular, commercial and non-commercial partners. MSM with only male partners reported lower CCU as compared to MSM with partners of both genders (47.3% and 62%, respectively, p = 0.11). CCU levels differed significantly by status of sex partner. Overall, MSM having 'men only' as partners and those with partners of mixed status have greater risk behaviour in terms of low CCU. HIV prevention interventions need to focus attention on men in 'exclusively male' sex partnerships as well as MSM with a mix of casual, regular and commercial partners.