Sexual frequency and planning among at-risk men who have sex with men in the United States: implications for event-based intermittent pre-exposure prophylaxis

The Disparities of PrEP Adherence Among Men Who Have Sex With Men Between the Global South and the Global North: An Updated Determinantal Global Meta-Analysis

BACKGROUND

Suboptimal adherence to pre-exposure prophylaxis (PrEP) limits its global impact, with current evidence mostly from the Global North and lacking Global South perspectives. This meta-analysis synthesizes the rates and determinants of suboptimal adherence to oral PrEP among men who have sex with men (MSM) in both regions.

METHODS

We searched for literature describing PrEP adherence and its determinants among MSM globally up until October 2024 to conduct a meta-analysis on the rate and determinants of suboptimal adherence in both regions. The definition of (sub-)optimal adherence was study based.

RESULTS

We included 82 studies in the meta-analysis, with 24, 53, and 5 stemmed from the Global South, North, and global multicenter studies, respectively. Oral PrEP suboptimal adherence is prevalent among MSM PrEP users globally (rate = 0.33, 95% confidence interval [CI]: 0.28 to 0.38) with a significantly higher rate ( P = 0.021) in the Global South (rate = 0.41, 95% CI: 0.33 to 0.50) than in the Global North (rate = 0.29, 95% CI: 0.23 to 0.35). In the Global South, older age (OR = 0.57, 95% CI: 0.37 to 0.87), alcohol use (OR = 1.28, 95% CI: 1.02 to 1.60), and presenting depressive symptoms (OR = 1.47, 95% CI: 1.01 to 2.16) were associated with suboptimal adherence. In the Global North, MSM self-identified as Black (OR = 2.27, 95% CI: 1.31 to 3.95) or Other (OR = 1.36, 95% CI: 1.02 to 1.81), having a university degree (OR = 0.50, 95% CI: 0.34 to 0.73), and presenting depressive symptoms (OR = 2.26, 95% CI: 1.35 to 3.78) were associated with suboptimal adherence. On-demand PrEP users globally demonstrated a higher likelihood of suboptimal adherence (OR = 1.59, 95% CI: 1.18 to 2.14).

CONCLUSIONS

Suboptimal adherence to oral PrEP is prevalent among MSM globally, particularly higher in the Global South. Regional differences in determinants highlight the need for tailored interventions. Tailored interventions are required to address mental health with tailored efforts to younger MSM in the Global South, while interventions in the Global North should be tailored to specific subgroups.

The Use of Daily and On-Demand Oral Pre-Exposure Prophylaxis Dosing Strategies Among Young Adult Gay, Bisexual and Other Men who have Sex with Men Enrolled in an mHealth Adherence Intervention

Pre-exposure prophylaxis (PrEP) is a highly effective HIV prevention option for gay, bisexual and other men who have sex with men (GBMSM). However, with newer PrEP options, a greater understanding of whether and why GBMSM switch dosing strategies is needed to inform clinical practice and research. We assessed the dosing strategies (daily or on-demand) of GBMSM enrolled in an mHealth PrEP adherence pilot intervention at four timepoints over approximately 10 months. Among GBMSM with complete data (n = 66), a consistent daily dosing strategy was used by most (73%) participants across all time points, while on-demand PrEP was used at least once during the study period by 27% of participants. A higher percentage of on-demand PrEP users self-reported as Asian/Pacific Islander and had less positive attitudes toward PrEP, adjusting for key sociodemographic variables and intervention arm. Daily PrEP users reported high numbers of sexual partners, and the primary reason that they would switch to on-demand PrEP is reduced sexual activity. At the final assessment, 75% of participants were taking daily PrEP, of whom 27% reported that they would like to switch to another option, including on-demand and long-acting injectable PrEP. While findings were largely descriptive, they showed that switches in PrEP dosing strategies are relatively common and PrEP strategy choice may vary across racial and ethnic groups.

Prediction of Sex and the Potential Use of On-Demand PrEP Among Young Men Who Have Sex With Men in the United States

BACKGROUND

On-demand dosing of preexposure prophylaxis (PrEP) requires accurate prediction of sex; however, prediction abilities among young men who have sex with men (YMSM) have not been characterized.

SETTING

A nationally recruited prospective cohort of YMSM ages 16-24 years.

METHODS

We followed 120 YMSM for 8 weeks using digital daily surveys (DDSs) to measure engagement in and prediction of anal sex over 24 hours, along with condom use and other encounter-level circumstances. Our main outcome, an "unpredicted spontaneous encounter," was defined as an anal sex encounter that occurred without sufficient prior knowledge to (hypothetically) enable protective on-demand PrEP use according to dosing guidelines. We operationalized this outcome as an anal sex encounter for which a participant indicated: (1) on the prior day's DDS that there was a low likelihood of sex occurring in the subsequent 24 hours (unpredicted) and (2) on the current day's DDS that he knew ≤2 hours in advance that the encounter would occur (spontaneous).

RESULTS

Approximately one-third of all anal sex encounters during the study period were unpredicted and spontaneous and would not have been protected (hypothetically) by on-demand dosing. More than two-thirds of participants experienced such an encounter and almost three-quarters of all acts were condomless.

CONCLUSIONS

On-demand PrEP to prevent HIV acquisition may be challenging for many YMSM. Clinical and public health approaches that account for patients' predictive abilities alongside their dosing preferences may help to optimize selection of and adherence to PrEP dosing strategies.

Mathematical modelling of the influence of serosorting on the population-level HIV transmission impact of pre-exposure prophylaxis

OBJECTIVES

HIV pre-exposure prophylaxis (PrEP) may change serosorting patterns. We examined the influence of serosorting on the population-level HIV transmission impact of PrEP, and how impact could change if PrEP users stopped serosorting.

DESIGN

We developed a compartmental HIV transmission model parameterized with bio-behavioural and HIV surveillance data among MSM in Canada.

METHODS

We separately fit the model with serosorting and without serosorting [counterfactual; sero-proportionate mixing (random partner-selection proportional to availability by HIV status)], and reproduced stable HIV epidemics with HIV-prevalence 10.3-24.8%, undiagnosed fraction 4.9-15.8% and treatment coverage 82.5-88.4%. We simulated PrEP-intervention reaching stable pre-specified coverage by year-one and compared absolute difference in relative HIV-incidence reduction 10 years post-intervention (PrEP-impact) between models with serosorting vs. sero-proportionate mixing; and counterfactual scenarios when PrEP users immediately stopped vs. continued serosorting. We examined sensitivity of results to PrEP-effectiveness (44-99%; reflecting varying dosing or adherence levels) and coverage (10-50%).

RESULTS

Models with serosorting predicted a larger PrEP-impact than models with sero-proportionate mixing under all PrEP-effectiveness and coverage assumptions [median (interquartile range): 8.1% (5.5-11.6%)]. PrEP users' stopping serosorting reduced PrEP-impact compared with when PrEP users continued serosorting: reductions in PrEP-impact were minimal [2.1% (1.4-3.4%)] under high PrEP-effectiveness (86-99%); however, could be considerable [10.9% (8.2-14.1%)] under low PrEP effectiveness (44%) and high coverage (30-50%).

CONCLUSION

Models assuming sero-proportionate mixing may underestimate population-level HIV-incidence reductions due to PrEP. PrEP-mediated changes in serosorting could lead to programmatically important reductions in PrEP-impact under low PrEP-effectiveness. Our findings suggest the need to monitor sexual mixing patterns to inform PrEP implementation and evaluation.

On-Demand Oral Pre-exposure Prophylaxis with Tenofovir/Emtricitabine: What Every Clinician Needs to Know

Based on the results of the IPERGAY study, on-demand HIV pre-exposure prophylaxis (PrEP; also known as "non-daily PrEP," "event-driven PrEP," or "2-1-1 PrEP") is being requested more frequently by patients who have intermittent sexual risk or are unable/unwilling to take daily PrEP; therefore, clinicians will be increasingly required to familiarize themselves with its appropriate use. In this perspective, we summarize data related to on-demand PrEP, describe advantages and disadvantages for this alternative dosing strategy, and provide clinical counseling points.

National trends in HIV pre-exposure prophylaxis awareness, willingness and use among United States men who have sex with men recruited online, 2013 through 2017

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is a key HIV prevention technology, and is a pillar of a comprehensive HIV prevention approach for men who have sex with men (MSM). Because there have been no national data to characterize trends in the PrEP continuum in the United States, overall and for key demographic groups of MSM, we aimed to describe the extent to which PrEP awareness, willingness and use changed over time, overall and for specific groups of MSM critical for HIV prevention (e.g. Black and Hispanic MSM, younger MSM, MSM in rural areas and MSM without health coverage).

METHODS

The American Men's Internet Survey (AMIS) is an annual survey of US MSM conducted in the United States among MSM aged ≥15 years since 2013. We analysed data on trends in elements of the PrEP continuum (awareness, willingness and use of PrEP) in a sample of 37,476 HIV-negative/unknown status MSM from December 2013 through November 2017. We evaluated trends in continuum steps overall and among demographic subgroups using Poisson models with Generalized Estimating Equations. For 2017 data, we used logistic regression to compare the prevalence of PrEP use among demographic groups.

RESULTS

Overall, 51.4% (n = 19,244) of AMIS respondents were PrEP-eligible across study years. Between 2013 and 2017, PrEP awareness increased from 47.4% to 80.6% willingness to use PrEP increased from 43.9% to 59.5% and PrEP use in the past 12 months increased from 1.7% to 19.9%. In 2017, use of PrEP was lower for men who were younger, lived outside of urban areas, and lacked health insurance; PrEP use was not different among Black, Hispanic and white MSM.

CONCLUSIONS

Our data show progress in use of PrEP among US MSM, but also reveal mismatches between PrEP use and epidemic need. We call for additional support of PrEP initiation, especially among young, non-urban and uninsured MSM. Black and Hispanic MSM report levels of PrEP use no different from white MSM, but given higher HIV incidence for Black and Hispanic MSM, parity in use is not sufficient for epidemic control or health equity.

Temporal Fluctuations in Behavior, Perceived HIV Risk, and Willingness to Use Pre-Exposure Prophylaxis (PrEP)

Individual perceptions of HIV risk influence willingness to use pre-exposure prophylaxis (PrEP) for HIV prevention. Among men who have sex with men (MSM) and male sex workers (MSWs), temporal or episodic changes in risk behavior may influence perceived risk and PrEP acceptability over time. We investigated fluctuations in perceived HIV risk and PrEP acceptability, comparing MSWs against MSM who do not engage in sex work. We conducted 8 focus groups (n = 38) and 56 individual interviews among MSM and MSWs in Providence, RI. Perceived HIV risk shaped willingness to use PrEP among both MSWs and MSM who did not engage in sex work, and risk perceptions changed over time depending on behavior. For MSWs, perceived risk cycled according to patterns of substance use and sex work activity. These cycles yielded an "access-interest paradox": an inverse relationship between willingness to use and ability to access PrEP. MSM who did not engage in sex work also reported temporal shifts in risk behavior, perceived risk, and willingness to use PrEP, but changes were unrelated to access. MSM attributed fluctuations to seasonal changes, vacations, partnerships, behavioral "phases," and episodic alcohol or drug use. Efforts to implement PrEP among MSM and street-based MSWs should address temporal changes in willingness to use PrEP, which are linked to perceived risk. Among MSWs, confronting the access-interest paradox may require intensive outreach during high-risk times and efforts to address low perceived risk during times of reduced sex work.

Are Anal Sex Roles Associated with Preferences for Pre-Exposure Prophylaxis Administration Modalities Among Men Who Have Sex with Men?

The current study sought to examine awareness of, willingness to use, and preferences for available and theoretical administration modalities for HIV pre-exposure prophylaxis (PrEP) and the association of anal sex roles with these concepts among a sample of men who have sex with men (MSM) in Paris, France. Broadcast advertisements were placed on a popular geosocial-networking smartphone application for MSM to direct users to complete a Web-based survey. MSM answered questions on their recent engagement in condomless anal intercourse and awareness of and willingness to use PrEP in the form of once daily and event-driven pill regimens, long-acting injections, and penile and rectal microbicides as well as sexual roles. Multinomial regression models were fit to assess the association between behaviorally classified anal sexual role and preferences for one of these biomedical prevention modalities. A total of 482 HIV-uninfected MSM completed the survey, 48.1% of whom engaged in some form of condomless anal intercourse in the preceding 3 months. Most respondents (85.3%) had heard of once daily PrEP, but fewer respondents had heard of other prevention strategies. Assuming equal effectiveness, long-acting injections were the most commonly preferred (21.8%). Behaviorally defined "bottom" and "versatile" MSM more frequently preferred long-acting injections (32.9% of "bottoms" and 25.3% of "versatiles"). The development of long-acting injections to deliver antiretroviral drugs and topical microbicides may offer more convenient and acceptable options for HIV prevention among MSM, as MSM in this sample were willing to use them and would prefer to use them over currently available pill regimens.

Daily or on-demand oral tenofovir disoproxil fumarate/emtricitabine for HIV pre-exposure prophylaxis: experience from a hospital-based clinic in France

BACKGROUND

On-demand oral tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) has been approved for pre-exposure prophylaxis (PrEP) in MSM in France following the results of clinical studies, but data are limited on real-world experience.

DESIGN

A single-center, open-label, prospective cohort study that recruited people at high risk of HIV infection in Paris.

METHODS

Participants were enrolled in a single hospital-based outpatient clinic and were proposed to start PrEP with daily or on demand TDF/FTC. At baseline and every 3 months thereafter, patients were tested for HIV and creatinine plasma levels, and data on sexual behavior, other sexually transmitted infections (STIs), and tolerability were collected.

RESULTS

From 10 November 2015 to 30 April 2017, 1069 patients were screened and 1049 (98.1%) started PrEP. Median age was 36 years, 99.4% were MSM with a median number of partners of 10, and 793 (75.6%) opted for on demand PrEP. Over 486 person-years of follow-up, four HIV-infections were diagnosed in poorly or nonadherent patients (incidence 0.82/100 person-years). Rate of condomless sex at last intercourse increased from 53.3% at baseline to 79% at month 12 (P < 10), but increase in bacterial STI rates was modest (14.6% at baseline vs. 19.2% at month 12; P < 10). Most adverse events were gastrointestinal and did not lead to PrEP discontinuation.

CONCLUSIONS

Most PrEP users were high-risk MSM and opted for on-demand PrEP. PrEP use was associated with a low HIV incidence and a high rate of condomless sex with a modest increase in bacterial STIs.

Development of an Agent-Based Model to Investigate the Impact of HIV Self-Testing Programs on Men Who Have Sex With Men in Atlanta and Seattle

BACKGROUND

In the United States HIV epidemic, men who have sex with men (MSM) remain the most profoundly affected group. Prevention science is increasingly being organized around HIV testing as a launch point into an HIV prevention continuum for MSM who are not living with HIV and into an HIV care continuum for MSM who are living with HIV. An increasing HIV testing frequency among MSM might decrease future HIV infections by linking men who are living with HIV to antiretroviral care, resulting in viral suppression. Distributing HIV self-test (HIVST) kits is a strategy aimed at increasing HIV testing. Our previous modeling work suggests that the impact of HIV self-tests on transmission dynamics will depend not only on the frequency of tests and testers' behaviors but also on the epidemiological and testing characteristics of the population.

OBJECTIVE

The objective of our study was to develop an agent-based model to inform public health strategies for promoting safe and effective HIV self-tests to decrease the HIV incidence among MSM in Atlanta, GA, and Seattle, WA, cities representing profoundly different epidemiological settings.

METHODS

We adapted and extended a network- and agent-based stochastic simulation model of HIV transmission dynamics that was developed and parameterized to investigate racial disparities in HIV prevalence among MSM in Atlanta. The extension comprised several activities: adding a new set of model parameters for Seattle MSM; adding new parameters for tester types (ie, regular, risk-based, opportunistic-only, or never testers); adding parameters for simplified pre-exposure prophylaxis uptake following negative results for HIV tests; and developing a conceptual framework for the ways in which the provision of HIV self-tests might change testing behaviors. We derived city-specific parameters from previous cohort and cross-sectional studies on MSM in Atlanta and Seattle. Each simulated population comprised 10,000 MSM and targeted HIV prevalences are equivalent to 28% and 11% in Atlanta and Seattle, respectively.

RESULTS

Previous studies provided sufficient data to estimate the model parameters representing nuanced HIV testing patterns and HIV self-test distribution. We calibrated the models to simulate the epidemics representing Atlanta and Seattle, including matching the expected stable HIV prevalence. The revised model facilitated the estimation of changes in 10-year HIV incidence based on counterfactual scenarios of HIV self-test distribution strategies and their impact on testing behaviors.

CONCLUSIONS

We demonstrated that the extension of an existing agent-based HIV transmission model was sufficient to simulate the HIV epidemics among MSM in Atlanta and Seattle, to accommodate a more nuanced depiction of HIV testing behaviors than previous models, and to serve as a platform to investigate how HIV self-tests might impact testing and HIV transmission patterns among MSM in Atlanta and Seattle. In our future studies, we will use the model to test how different HIV self-test distribution strategies might affect HIV incidence among MSM.

Maximizing the Benefits of HIV Preexposure Prophylaxis

Preexposure prophylaxis (PrEP) with tenofovir/emtricitabine (slash indicates coformulation) is highly effective in preventing new HIV infections. PrEP efficacy is strongly associated with adherence. In clinical trials, PrEP has been more effective in men who have sex with men and HIV-serodiscordant heterosexual couples than in women, likely reflecting pharmacokinetic differences between levels of tenofovir disoproxil fumarate in vaginal and rectal tissues, and poorer adherence in studies in women. Current guidelines recommend daily PrEP for men and women; however, PrEP taken at least 4 days per week for men may be as effective as daily PrEP, and women must take PrEP 6 to 7 days per week to maximize efficacy. Data are accumulating on the effectiveness of pericoital PrEP for men who have sex with men, but it is not yet recommended in the United States. PrEP is underprescribed for younger individuals, black individuals, and Hispanic and Latino individuals. This article summarizes a presentation by Susan P. Buchbinder, MD, at the IAS-USA continuing education program, Improving the Management of HIV Disease, held in Chicago, Illinois, in May 2017.

In what circumstances could nondaily preexposure prophylaxis for HIV substantially reduce program costs?

Supplemental Digital Content is available in the text

Objectives:

To review the main factors influencing the costs of nondaily oral preexposure prophylaxis (PrEP) with tenofovir (±emtricitabine). To estimate the cost reductions possible with nondaily PrEP compared with daily PrEP for different populations (MSM and heterosexual populations).

Design:

Systematic review and data triangulation.

Methods:

We estimated the required number of tablets/person/week for dosing regimens used in the HPTN 067/ADAPT (daily/time-driven/event-driven) and IPERGAY (on-demand) trials for different patterns of sexual intercourse. Using trial data, and behavioural and cost data obtained through systematic literature reviews, we estimated cost savings resulting from tablet reductions for nondaily versus daily oral PrEP, assuming 100% adherence.

Results:

Among different populations being prioritized for PrEP, the median reported number of days of sexual activity varied between 0 and 2 days/week (0–1.5 days/week for MSM, 1–2 days/week for heterosexual populations). With 100% adherence and two or fewer sex-days/week, HPTN 067/ADAPT nondaily regimens reduced the number of tablets/week by more than 40% compared with daily PrEP. PrEP program costs were reduced the most in settings with high drug costs, for example, by 66–69% with event-driven PrEP for French/US populations reporting on average one sex-day/week.

Conclusion:

Nondaily oral PrEP could lower costs substantially (>50%) compared with daily PrEP, particularly in high-income countries. Adherence and efficacy data are needed to determine cost-effectiveness.

Preexposure Prophylaxis Modality Preferences Among Men Who Have Sex With Men and Use Social Media in the United States

Background

Preexposure prophylaxis (PrEP) is available as a daily pill for preventing infection with the human immunodeficiency virus (HIV). Innovative methods of administering PrEP systemically or topically are being discussed and developed.

Objective

The objective of our study was to assess attitudes toward different experimental modalities of PrEP administration.

Methods

From April to July 2015, we recruited 1106 HIV-negative men who have sex with men through online social media advertisements and surveyed them about their likelihood of using different PrEP modalities. Participants responded to 5-point Likert-scale items indicating how likely they were to use each of the following PrEP modalities: a daily oral pill, on-demand pills, periodic injection, penile gel (either before or after intercourse), rectal gel (before/after), and rectal suppository (before/after). We used Wilcoxon signed rank tests to determine whether the stated likelihood of using any modality differed from daily oral PrEP. Related items were combined to assess differences in likelihood of use based on tissue or time of administration. Participants also ranked their interest in using each modality, and we used the modified Borda count method to determine consensual rankings.

Results

Most participants indicated they would be somewhat likely or very likely to use PrEP as an on-demand pill (685/1105, 61.99%), daily oral pill (528/1036, 50.97%), injection (575/1091, 52.70%), or penile gel (438/755, 58.01% before intercourse; 408/751, 54.33% after). The stated likelihoods of using on-demand pills (median score 4) and of using a penile gel before intercourse (median 4) were both higher than that of using a daily oral pill (median 4, P<.001 and P=.001, respectively). Compared with a daily oral pill, participants reported a significantly lower likelihood of using any of the 4 rectal modalities (Wilcoxon signed rank test, all P<.001). On 10-point Likert scales created by combining application methods, the reported likelihood of using a penile gel (median 7) was higher than that of using a rectal gel (median 6, P<.001), which was higher than the likelihood of using a rectal suppository (median 6, P<.001). The modified Borda count ranked on-demand pills as the most preferred modality. There was no difference in likelihood of use of PrEP (gel or suppository) before or after intercourse.

Conclusions

Participants typically prefer systemic PrEP and are less likely to use a modality that is administered rectally. Although most of these modalities are seen as favorable or neutral, attitudes may change as information about efficacy and application becomes available. Further data on modality preference across risk groups will better inform PrEP development.

Sexual Behavior Patterns and PrEP Dosing Preferences in a Large Sample of North American Men Who Have Sex With Men

INTRODUCTION

Pre-exposure prophylaxis (PrEP), taken as a single daily coformulated pill containing tenofovir -emtricitabine, is a promising intervention to reduce the likelihood of HIV acquisition in at-risk individuals, including men who have sex with men. Little is known about the acceptability of less than daily, intermittent PrEP regimens.

METHODS

We conducted an online survey of North American men who have sex with men to characterize their sexual frequency and planning behaviors and correlate these with PrEP dosing preferences.

RESULTS

Of the 3217 respondents who completed the survey, 46% reported engaging in unplanned condomless anal intercourse (CAI) at least once in previous 3 months and 8% reported engaging in CAI more than once per week. In multivariable analysis, reporting unplanned CAI was associated with lower educational level, identifying as homosexual/gay as compared with bisexual, being in a monogamous relationship, having a higher self-perceived risk of HIV acquisition, reporting higher income, engaging in CAI more than five times in the last 3 months, and not having visited a health care provider in the previous year. Frequent CAI (>1 time per week) was associated with being younger, identifying as homosexual/gay as compared with bisexual, being in a monogamous relationship, and having a higher self-perceived risk of HIV. Having only planned sex over the last 3 months was associated with a preference for event-based PrEP, whereas having frequent or unplanned CAI was associated with a preference for daily or time-driven PrEP regimens, respectively.

CONCLUSION

Our findings suggest that preferences for different PrEP regimens are associated with the sexual frequency and planning behaviors of potential users.

Nondaily preexposure prophylaxis for HIV prevention

PURPOSE OF REVIEW

To discuss nondaily preexposure prophylaxis (PrEP) modalities that may provide advantages compared with daily PrEP in cost and cumulative toxicity, but may have lower adherence forgiveness.

RECENT FINDINGS

Animal models have informed our understanding of early viral transmission events, which help guide event-driven PrEP dosing strategies. These models indicate early establishment of viral replication in rectal or cervicovaginal tissues, so event-driven PrEP should rapidly deliver high mucosal drug concentrations within hours of the potential exposure event. Macaque models have demonstrated the high biological efficacy for event-driven dosing of oral tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) against both vaginal and rectal virus transmission. In humans, the IPERGAY study demonstrated 86% efficacy for event-driven oral TDF/FTC dosing among men who have sex with men (MSM), while no similar efficacy data are available on women or heterosexual men. The HPTN 067 study showed that certain MSM populations adhere well to nondaily PrEP, whereas other populations of women adhere more poorly to nondaily versus daily regimens. Pharmacokinetic studies following oral TDF/FTC dosing in humans indicate that TFV-diphosphate (the active form of TFV) accumulates to higher concentrations in rectal versus cervicovaginal tissue, but nonadherence in trials complicates the interpretation of differential mucosal drug concentrations.

SUMMARY

Event-driven dosing for TFV-based PrEP has promise for HIV prevention in MSM. Future research of event-driven PrEP in women and heterosexual men should be guided by a better understanding of the importance of mucosal drug concentrations for PrEP efficacy and its sensitivity to adherence.

Are Clade Specific HIV Vaccines a Necessity? An Analysis Based on Mathematical Models

As HIV-1 envelope immune responses are critical to vaccine related protection, most candidate HIV vaccines entering efficacy trials are based upon a clade specific design. This need for clade specific vaccine prototypes markedly reduces the implementation of potentially effective HIV vaccines. We utilized a mathematical model to determine the effectiveness of immediate roll-out of a non-clade matched vaccine with reduced efficacy compared to constructing clade specific vaccines, which would take considerable time to manufacture and test in safety and efficacy trials. We simulated the HIV epidemic in San Francisco (SF) and South Africa (SA) and projected effectiveness of three vaccination strategies: i) immediate intervention with a 20–40% vaccine efficacy (VE) non-matched vaccine, ii) delayed intervention by developing a 50% VE clade-specific vaccine, and iii) immediate intervention with a non-matched vaccine replaced by a clade-specific vaccine when developed. Immediate vaccination with a non-clade matched vaccine, even with reduced efficacy, would prevent thousands of new infections in SF and millions in SA over 30 years. Vaccination with 50% VE delayed for five years needs six and 12 years in SA to break-even with immediate 20 and 30% VE vaccination, respectively, while not able to surpass the impact of immediate 40% VE vaccination over 30 years. Replacing a 30% VE with a 50% VE vaccine after 5 years reduces the HIV acquisition by 5% compared to delayed vaccination. The immediate use of an HIV vaccine with reduced VE in high risk communities appears desirable over a short time line but higher VE should be the pursued to achieve strong long-term impact. Our analysis illustrates the importance of developing surrogate markers (correlates of protection) to allow bridging types of immunogenicity studies to support more rapid assessment of clade specific vaccines.

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Rapid deployment of non-clade matched HIV vaccines would be an effective public-health strategy in high risk populations.

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Pursuit of further incremental increase in vaccine efficacy is justified and will result in better long term effectiveness.

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Reduced condom use by vaccinated individuals may diminish the advantage of the replacement vaccination strategy.

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Reliable surrogate markers of vaccine efficacy are needed to speed up the development of effective HIV vaccines.

The HIV vaccine field has followed the concept of clade specific (clade matched) vaccines for over 30 years. We investigate the implementation of non-clade matched and clade specific vaccines by simulating the HIV epidemics in San Francisco and South Africa: two regions of the world where the epidemics are well characterized. Our analysis suggests that rapid deployment of a non-clade matched vaccine would be an effective public health strategy. The most effective 10-year vaccination strategy is to employ non-clade matched vaccines in highest risk populations followed by the rapid development of a more effective clade matched prototype.

Accuracy of highly sexually active gay and bisexual men's predictions of their daily likelihood of anal sex and its relevance for intermittent event-driven HIV pre-exposure prophylaxis

OBJECTIVE

We sought to examine highly sexually active gay and bisexual men's accuracy in predicting their sexual behavior for the purposes of informing future research on intermittent event-driven HIV Pre-Exposure Prophylaxis.

DESIGN

For 30 days, 92 HIV-negative men completed a daily survey about their sexual behavior (n = 1688 days of data) and indicated their likelihood of having anal sex with a casual male partner next day.

METHOD

We used multilevel modeling to analyze the association between self-reported likelihood of and subsequent engagement in anal sex.

RESULTS

We found a linear association between men's reported likelihood of anal sex with casual partners and the actual probability of engaging in sex, although men overestimated the likelihood of sex. Overall, we found that men were better at predicting when they would not have sex than when they would, particularly if any likelihood value greater than 0% was treated as indicative that sex might occur. We found no evidence that men's accuracy of prediction was affected by whether it was a weekend or whether they were using substances, although both did increase the probability of sex.

DISCUSSION

These results suggested that, men taking event-driven intermittent Pre-Exposure Prophylaxis, 14% of doses could have been safely skipped with a minimal rate of false negatives using guidelines of taking a dose unless there was no chance (ie, 0% likelihood) of sex on next day. This would result in savings of over US $1300 per year in medication costs per participant.

Medication adherence among men who have sex with men at risk for HIV infection in the United States: implications for pre-exposure prophylaxis implementation

Pre-exposure prophylaxis (PrEP) is a promising HIV prevention approach for men who have sex with men (MSM), however non-adherence could limit its effectiveness. Understanding the experiences of HIV-uninfected MSM taking routine medications can provide valuable insights into open label PrEP adherence in real world settings and guide development of PrEP adherence interventions. In this study, we examined self-reported medication-taking experiences and facilitators and barriers of medication adherence among a geographically-diverse online sample of HIV-uninfected US MSM. Among 1480 participants, 806 (54%) reported taking medications regularly, of whom 80% reported taking medications for treatment and 55% for prevention purposes. Facilitators of medication adherence included establishing a routine, keeping medication visible, and using a pill-box; barriers included forgetting, changes in routine, and being busy or away from home. Only 45% rated their medication-taking ability as excellent, and 36% reported not missing any doses in the past 30 days. In multivariable analyses, older men and those not reporting any adherence barriers were more likely to report excellent adherence, and men willing to use PrEP were more likely to report perfect 30-day adherence. Counseling strategies to build pill-taking routines and support younger MSM are suggested to maximize the public health impact of PrEP.

HIV transmission among men who have sex with men due to condom failure

Background

Despite preventive efforts, HIV incidence remains high among men who have sex with men (MSM) in industrialized countries. Condoms are an important element in prevention but, given the high frequency of condom use and their imperfect effectiveness, a substantial number and proportion of HIV transmissions may occur despite condoms. We developed a model to examine this hypothesis.

Methods

We used estimates of annual prevalent and incident HIV infections for MSM in Ontario. For HIV-negative men, we applied frequencies of sexual episodes and per-contact HIV transmission risks of receptive and insertive anal sex with and without a condom and oral sex without a condom. We factored in the proportion of HIV-infected partners receiving antiretroviral therapy and its impact in reducing transmissibility. We used Monte-Carlo simulation to determine the plausible range for the proportion of HIV transmissions for each sexual practice.

Results

Among Ontario MSM in 2009, an estimated 92,963 HIV-negative men had 1,184,343 episodes of anal sex with a condom and 117,133 anal sex acts without a condom with an HIV-positive partner. Of the 693 new HIV infections, 51% were through anal sex with a condom, 33% anal sex without a condom and 16% oral sex. For anal sex with a condom, the 95% confidence limits were 17% and 77%.

Conclusions

The proportion of HIV infections related to condom failure appears substantial and higher than previously thought. That 51% of transmissions occur despite condom use may be conservative (i.e. low) since we used a relatively high estimate (87.1%) for condom effectiveness. If condom effectiveness were closer to 70%, a value estimated from a recent CDC study, the number and proportion of HIV transmissions occurring despite condom use would be much higher. Therefore, while condom use should continue to be promoted and enhanced, this alone is unlikely to stem the tide of HIV infection among MSM.

Preferences for daily or intermittent pre-exposure prophylaxis regimens and ability to anticipate sex among HIV uninfected members of Kenyan HIV serodiscordant couples

Intermittent dosing for pre-exposure prophylaxis (PrEP) has been proposed as an alternative to daily PrEP to reduce cost and patient drug exposure and to improve adherence. One possible dosing regimen is pre-intercourse PrEP, which requires anticipating sex in advance. We examined preferences for daily versus pre-intercourse PrEP and ability to anticipate sex among 310 HIV uninfected members of HIV serodiscordant heterosexual couples in Thika, Kenya, with high HIV knowledge and experience with daily PrEP use in a clinical trial setting. Preferences were evenly split between daily PrEP (47.4 %) and pre-intercourse PrEP (50.7 %). Participants were more likely to prefer daily PrEP if they reported unprotected sex during the prior month (adjusted prevalence ratio [aPR] 1.48, 95 % CI 1.20-1.81) or <80 % adherence to study drug (aPR 1.50, 95 % CI 1.25-1.79), and were less likely to prefer daily PrEP if sex was usually planned, versus spontaneous (aPR 0.76, 95 % CI 0.61-0.96). A minority (24.2 %) reported anticipating sex >3 h in advance, with younger participants being less likely to do so (aPR 0.43, 95 % CI 0.23-0.83 for ages 18-29 vs. ≥40). Findings suggest that intermittent PrEP could be a popular option in this population, but that optimal adherence and sufficient drug levels might be challenging with a pre-intercourse regimen.

Pharmacokinetics of single- and multiple-dose emtricitabine in healthy male Chinese volunteers

Emtricitabine (FTC) is used for the treatment of HIV infection and pre-exposure chemoprophylaxis. It is often used in combination with tenofovir disoproxil fumarate (TDF). This study was designed to evaluate FTC pharmacokinetics in healthy male Chinese volunteers. Sixty subjects were recruited into this single-centre, randomised, open-label study and randomly received single (groups A, B and C) or multiple oral doses (once daily for 6 days; groups D, E and F) of 200-mg FTC capsules alone (A and D), or combined with 300-mg TDF tablets (B and E), or 200 mg of FTC plus 300 mg of TDF with a high-fat diet (C and F), respectively. FTC was well-tolerated in all groups. After a single dose, there were no differences in the mean AUC0-∞ values; however, there were significant differences in the mean Tmax values (1.05, 1.40 and 2.10 h for groups A, B and C, respectively; p < 0.05). In the multiple-dose study, our results were significantly different from published t1/2 values following single-dose FTC.

Strong propensity for HIV transmission among men who have sex with men in Vietnam: behavioural data and sexual network modelling

OBJECTIVES

Survey data from men who have sex with men (MSM) in Asian cities indicate ongoing and drastic increases in HIV prevalence. It is unknown which behavioural factors are most important in driving these epidemics. We aimed to analyse detailed sexual behaviour data among MSM in Vietnam and to model HIV transmission using improved assumptions on sexual network structure.

SETTING

Vietnam.

PARTICIPANTS

Internet-using men who had ever had sex (any type) with a man, aged ≥18 years and living in Vietnam. The study was cross-sectional, population-based and performed in 2012, using online respondent-driven sampling. The Internet-based survey instrument was completed by 982 participants, of which 857 were eligible. Questions included sociodemography and retrospective sexual behaviour, including number of unprotected anal sex (UAS) acts per partner.

PRIMARY AND SECONDARY OUTCOME MEASURES

Estimated basic reproductive number over 3 months as a function of transmission risk per UAS act; frequency distributions of number of UAS partners and UAS acts during last 3 months.

RESULTS

36% (CI 32% to 42%) reported UAS at least once during the last 3 months. 36% (CI 32% to 41%) had ever taken an HIV test and received the result. UAS partner numbers and number of UAS acts were both highly skewed and positively correlated. Using a weighted configuration model, taking into account partner numbers, frequency of UAS and their correlations, we estimated the basic reproductive number (R0) over 3 months. The results indicated rapid transmission over a wide range of values of per-act transmissibility.

CONCLUSIONS

Men with multiple partners had unexpectedly high UAS frequency per partner, paired with low HIV testing rates. The study highlights the importance of collecting data on frequency of UAS acts and indicates the need to rapidly scale-up HIV prevention services and testing opportunities for MSM in Vietnam.

Tenofovir-based HIV pre-exposure prophylaxis

HIV pre-exposure prophylaxis (PrEP) with daily oral tenofovir disoproxil fumarate (TDF) or TDF–emtricitabine (FTC) has been shown to be effective against sexual and injection-drug related HIV acquisition in four out of six large clinical trials. This article reviews the pharmacology of TDF and FTC as it relates both to PrEP efficacy and the emergence of viral resistance, summarizes the six trials and the inherent challenges to PrEP they highlighted, and proposes some future areas for further exploration.

Challenges and opportunities for oral pre-exposure prophylaxis in the prevention of HIV infection: where are we in Europe?

Following US Food and Drugs Administration approval in July 2012 of daily oral tenofovir and emtricitabine for pre-exposure prophylaxis (PrEP) to prevent HIV infection in high-risk individuals in the USA, there has been much controversy about the implementation of this PrEP regimen in other countries throughout the world, and in Europe in particular. In this review, we focus on the challenges and opportunities of a daily oral PrEP regimen to curb the rising incidence of HIV infection in high-risk groups, and particularly in men who have sex with men. A number of issues would need to be addressed before PrEP could be implemented, including assessing the real effectiveness and cost-effectiveness of daily PrEP, the sustainability of daily adherence, the risk of selecting resistance, the long-term safety, and the risk of change in sexual behavior that might offset the benefit of PrEP. Alternatives to a daily oral PrEP regimen are being explored.