Shifts in condom use following microbicide introduction: should we be concerned?

Infectious Disease Modelling of HIV Prevention Interventions: A Systematic Review and Narrative Synthesis of Compartmental Models

BACKGROUND

The HIV epidemic remains a major public health problem. Critical to transmission control are HIV prevention strategies with new interventions continuing to be developed. Mathematical models are important for understanding the potential impact of these interventions and supporting policy decisions. This systematic review aims to answer the following question: when a new HIV prevention intervention is being considered or designed, what information regarding it is necessary to include in a compartmental model to provide useful insights to policy makers? The primary objective of this review is therefore to assess suitability of current compartmental HIV prevention models for informing policy development.

METHODS

Articles published in EMBASE, Medline, Econlit, and Global Health were screened. Included studies were identified using permutations of (i) HIV, (ii) pre-exposure prophylaxis (PrEP), circumcision (both voluntary male circumcision [VMMC] and early-infant male circumcision [EIMC]), and vaccination, and (iii) modelling. Data extraction focused on study design, model structure, and intervention incorporation into models. Article quality was assessed using the TRACE (TRAnsparent and Comprehensive Ecological modelling documentation) criteria for mathematical models.

RESULTS

Of 837 articles screened, 48 articles were included in the review, with 32 unique mathematical models identified. The substantial majority of studies included PrEP (83%), whilst fewer modelled circumcision (54%), and only a few focussed on vaccination (10%). Data evaluation, implementation verification, and model output corroboration were identified as areas of poorer model quality. Parameters commonly included in the mathematical models were intervention uptake and effectiveness, with additional intervention-specific common parameters identified. We identified key modelling gaps; critically, models insufficiently incorporate multiple interventions acting simultaneously. Additionally, population subgroups were generally poorly represented-with future models requiring improved incorporation of ethnicity and sexual risk group stratification-and many models contained inappropriate data in parameterisation which will affect output accuracy.

CONCLUSIONS

This review identified gaps in compartmental models to date and suggests areas of improvement for models focusing on new prevention interventions. Resolution of such gaps within future models will ensure greater robustness and transparency, and enable more accurate assessment of the impact that new interventions may have, thereby providing more meaningful guidance to policy makers.

Safety Assessment of Microbicide 2P23 on the Rectal and Vaginal Microbiota and Its Antiviral Activity on HIV Infection

Containment of the AIDS pandemic requires reducing HIV transmission. HIV infection is initiated by the fusion of the membrane between the virus and the cell membrane of the host. 2P23 is an effective HIV membrane fusion inhibitor that may be a good entry inhibitor microbicide candidate. This study evaluated the potential of using gel-formulated 2P23 as a topical microbicide to prevent sexual transmission of HIV in the rectum and vagina. Our data revealed that 2P23 formulated in gel is effective against HIV. There was no change in antiviral activity at 25°C for 4 months or 60°C for 1 week. In addition, we demonstrated that the 2P23 gel was stable and fully functional at pH 4.0-8.0 and under different concentrations of H2O2. Finally, the 2P23 gel exhibited no cytotoxicity or antimicrobial activity and did not induce inflammatory changes in the rectal or vaginal mucosal epithelium in New Zealand rabbits after 20 mg/day daily rectovaginal application for 14 consecutive days. Despite repeated tissue sampling and 2P23 gel treatment, the inflammatory cytokines and microbiota of the rectum and vagina remained stable. These results add to general knowledge on the in vivo evaluation of anti-HIV microbicide application concerning inflammatory cytokines and microbiota changes in the rectum and vagina. These findings suggest that the 2P23 gel is an excellent candidate for further development as a safe and effective pre-exposure prophylactic microbicide for the prevention of HIV transmission.

Is modelling complexity always needed? Insights from modelling PrEP introduction in South Africa

BACKGROUND

Mathematical models can be powerful policymaking tools. Simple, static models are user-friendly for policymakers. More complex, dynamic models account for time-dependent changes but are complicated to understand and produce. Under which conditions are static models adequate? We compare static and dynamic model predictions of whether behavioural disinhibition could undermine the impact of HIV pre-exposure prophylaxis (PrEP) provision to female sex workers in South Africa.

METHODS

A static model of HIV risk was developed and adapted into a dynamic model. Both models were used to estimate the possible reduction in condom use, following PrEP introduction, without increasing HIV risk. The results were compared over a 20-year time horizon, in two contexts: at epidemic equilibrium and during an increasing epidemic.

RESULTS

Over time horizons of up to 5 years, the models are consistent. Over longer timeframes, the static model overstates the tolerated reduction in condom use where initial condom use is reasonably high ($\ge$50%) and/or PrEP effectiveness is low ($\le$45%), especially during an increasing epidemic.

CONCLUSIONS

Static models can provide useful deductions to guide policymaking around the introduction of a new HIV intervention over short-medium time horizons of up to 5 years. Over longer timeframes, static models may not sufficiently emphasise situations of programmatic importance, especially where underlying epidemics are still increasing.

Modelling the effect of market forces on the impact of introducing human immunodeficiency virus pre-exposure prophylaxis among female sex workers

Pre-exposure prophylaxis (PrEP) to prevent human immunodeficiency virus (HIV) enables female sex workers (FSWs) to protect themselves from HIV without relying on clients using condoms. Yet, because PrEP reduces HIV risk, financial incentives to not use condoms may lead to risk compensation: reductions in condom use and/or increases in commercial sex, and may reduce the price of unprotected sex. In this analysis, we integrate market forces into a dynamic HIV transmission model to assess how risk compensation could change the impact of PrEP among FSWs and clients. We parameterise how sexual behavior may change with PrEP use among FSWs using stated preference data combined with economic theory. Our projections suggest the impact of PrEP is sensitive to risk compensatory behaviors driven by changes in the economics of sex work. Condom substitution could reduce the impact of PrEP on HIV incidence by 55%, while increases in the frequency of commercial sex to counter decreases in the price charged for unprotected sex among PrEP users could entirely mitigate the impact of PrEP. Accounting for competition between PrEP users and nonusers exacerbates this further. Alternative scenarios where increases in unprotected sex among PrEP users are balanced by decreases in non-PrEP users have the opposite effect, resulting in PrEP having much greater impact. Intervention studies need to determine how HIV prevention products may change the economics of sex work and provision of unprotected sex to enable a better understanding of their impact.

The effect of HIV prevention products on incentives to supply condomless commercial sex among female sex workers in South Africa

Evidence suggests that economic factors play an important role in commercial sex work, in particular that condomless sex commands a price premium relative to condom-protected sex. This paper explores whether the use of a new HIV prevention product, with 100% efficacy but modeled after pre-exposure prophylaxis (PrEP), could change the price and quantity of condomless commercial sex supplied. We collected stated preference data from 122 HIV-negative female sex workers in urban South Africa, using a repeated choice experiment to simulate the impact of using PrEP on choices. Results suggest that the price premium for condomless sex would decrease by 73% with PrEP use and the quantity of condomless sex is predicted to increase by a factor of 2.27. Act price does not significantly affect choices without protection but strongly influences choices under full HIV protection. The utility offered by condoms reduces by around 15% under PrEP use. Because new HIV prevention products do not protect against other STIs or pregnancy, the unintended consequences of introducing HIV prevention products should be closely monitored, whereas users should not face stigma or blame for reacting rationally to exogenous changes to market conditions.

Nanotechnology and the future of condoms in the prevention of sexually transmitted infections

Objective

The human immunodeficiency virus (HIV) is among the utmost destructive viruses humankind has ever faced in almost four decades. It carries with it profound socioeconomic and public health implications. Unfortunately, there is, currently, no effective cure for HIV infections. This review discusses the various types of condoms, microbicides, and the potential use of nanoparticle-coated condoms as a means of diminishing the risk of HIV transmission and sexually transmitted infections (STIs) during sexual intercourse.

Methods

We identified 153 articles from 1989 to 2015 indexed in various journal platforms, reports, and magazines. Using the PRISMA guidelines as proxy in performing the research review process, only 53 articles were selected. Ideally, articles that failed to describe the nature and types of condoms, condom failures, nanoparticle-coated condoms, microbicides, and HIV prevention were excluded.

Results and Discussion

In general, it has been shown that antiretroviral therapy (ART) currently available can only limit transmission and acquisition of HIV strains. Apart from ART treatment, the use of condoms has been identified globally as a cost-effective intervention for reducing the spread of HIV and other STIs. However, while condoms are supposed to be effective, reliable, and easy to use, research has shown that they are attributable to 20% failures including breakages. Nevertheless, other studies have shown that coating condoms with nanoparticles is an important and effective method for reducing condom breakage and HIV/STI transmission during sexual intercourse.

Conclusions

A review of literature cited in this paper has shown that nanotechnology-based condom systems have the potential to prevent the spread of HIV and STIs. Furthermore, the antimicrobial nature of some nanoparticles could provide a safe and efficient way to disrupt and/or inactivate different STIs - including viral, bacterial, and fungal diseases.

When are declines in condom use while using PrEP a concern? Modelling insights from a Hillbrow, South Africa case study

INTRODUCTION

Oral pre-exposure prophylaxis (PrEP) is a promising new prevention approach for those most at risk of HIV infection. However, there are concerns that behavioural disinhibition, specifically reductions in condom use, might limit PrEP's protective effect. This study uses the case of female sex workers (FSWs) in Johannesburg, South Africa, to assess whether decreased levels of condom use following the introduction of PrEP may limit HIV risk reduction.

METHOD

We developed a static model of HIV risk and compared HIV-risk estimates before and after the introduction of PrEP to determine the maximum tolerated reductions in condom use with regular partners and clients for HIV risk not to change. The model incorporated the effects of increased STI exposure owing to decreased condom use. Noting that condom use with regular partners is generally low, we also estimated the change in condom use tolerated with clients only, to still achieve 50 and 90% risk reduction on PrEP. The model was parameterized using data from Hillbrow, Johannesburg. Sensitivity analyses were performed to ascertain the robustness of our results.

RESULTS

Reductions in condom use could be tolerated by FSWs with lower baseline condom use (65%). For scenarios where 75% PrEP effectiveness is attained, 50% HIV-risk reduction on PrEP would be possible even with 100% reduction in condom use from consistent condom use as high as 70% with clients. Increased exposure to STIs through reductions in condom use had limited effect on the reductions in condom use tolerated for HIV risk not to increase on PrEP.

CONCLUSIONS

PrEP is likely to be of benefit in reducing HIV risk, even if reductions in condom use do occur. Efforts to promote consistent condom use will be critical for FSWs with high initial levels of condom use, but with challenges in adhering to PrEP.

Condom migration after introduction of pre-exposure prophylaxis among HIV-uninfected adolescents in South Africa: A cohort analysis

Background

Approximately 3 million adolescents and young adults (AYA), between the ages of 15 years and 24 years, are living with HIV in sub-Saharan Africa. The use of pre-exposure prophylaxis (PrEP) may be a promising HIV prevention tool to bridge the high-risk years of AYA between sexual debut and adulthood.

Objectives

Concerns have been raised that the use of PrEP could lead to an increase in sexual risk behaviour and sexually transmitted infections in general and less condom use in particular among adolescents.

Methods

This study assesses condom use among South African adolescents enrolled on a demonstration PrEP study, called Pluspills, being conducted in Cape Town and Soweto. A questionnaire on sexual risk behaviour was administered at baseline and after 4, 8 and 12 weeks. Three different questions on condom use were asked at each visit. Unless all answers indicated condom use at all times, a participant was scored ‘at risk’. McNemar’s tests and a Cochran’s Q test were used to investigate changes in condom use over time.

Results

We interviewed 148 adolescents (66% female) at baseline. Eighty-nine participants completed all visits. In this group, an increase in condom use was observed over the period of 12 weeks. Most participants who reported behavioural changes mentioned an increase in condom use.

Conclusion

There was no sign of sexual risk compensation in the 12 weeks of the study. Observed increase in condom use can be explained by an increased awareness of personal HIV risk or by social desirability or recall biases. In future research, additional data including other biomarkers of unprotected sex and longer follow-up time would be useful to help understand the relationship between PrEP use, sexual risk perception and consequent behaviours, especially in adolescents.

Divergent Preferences for HIV Prevention: A Discrete Choice Experiment for Multipurpose HIV Prevention Products in South Africa

BACKGROUND

The development of antiretroviral (ARV)-based prevention products has the potential to substantially change the HIV prevention landscape; yet, little is known about how appealing these products will be outside of clinical trials, as compared with the existing options.

METHODS

We conducted a discrete choice experiment (DCE) to measure preferences for 5 new products among 4 important populations in the HIV response: adult men and women in the general population (aged 18 to 49 y), adolescent girls (aged 16 to 17 y), and self-identifying female sex workers (aged 18 to 49 y). We interviewed 661 self-reported HIV-negative participants in peri-urban South Africa, who were asked to choose between 3 unique, hypothetical products over 10 choice sets. Data were analyzed using multinomial, latent class and mixed multinomial logit models.

RESULTS

HIV protection was the most important attribute to respondents; however, results indicate significant demand among all groups for multipurpose prevention products that offer protection from HIV infection, other STIs, and unwanted pregnancy. All groups demonstrated a strong preference for long-lasting injectable products. There was substantial heterogeneity in preferences within and across population groups.

LIMITATIONS

Hypothetical DCE data may not mirror real-world choices, and products will have more attributes in reality than represented in choice tasks. Background data on participants, including sensitive areas of HIV status and condom use, was self-reported.

CONCLUSIONS

These results suggest that stimulating demand for new HIV prevention products may require a more a nuanced approach than simply developing highly effective products. No single product is likely to be equally attractive or acceptable across different groups. This study strengthens the call for effective and attractive multipurpose prevention products to be deployed as part of a comprehensive combination prevention strategy.

Evaluation of Sexual Risk Behavior Among Study Participants in the TDF2 PrEP Study Among Heterosexual Adults in Botswana

OBJECTIVE

Among participants of a clinical trial to test the efficacy of tenofovir/emtricitabine in protecting heterosexual men and women living in Botswana from HIV infection, the aim was to determine (1) if sexual risk behavior, specifically condomless sex acts and number of sex partners, changed over time, (2) factors associated with condomless sex acts and number of sex partners, and (3) the effect of participant treatment arm perception on risk behavior to address the possibility of risk compensation.

METHODS

A longitudinal modeling of rates of risk behaviors was used to determine if the rate of condomless sex acts (#acts/person) and rate of sex partners (#partners/person) changed over time and which factors were associated with behavior change.

RESULTS

One thousand two hundred participants were analyzed over 1 year. There was a 25% decrease in the rate of sex partners among participants sexually active in the last 30 days. The rate of reported condomless sex acts was greater for males [rate ratio (RR) = 1.34; confidence interval (CI): 1.07 to 1.67] and participants whose sexual debut in years was ≤15 years of age (RR = 1.65; CI: 1.14 to 2.38) and 16-17 (RR = 1.68; CI: 1.22 to 2.31) compared with those ≥20 years. Rate of reported sex partners was greater for males (RR = 3.67; CI: 2.86 to 4.71) and participants whose age at sexual debut in years was ≤15 (RR = 2.92; CI: 2.01 to 4.22) and 16-17 (RR = 2.34; CI: 1.69 to 3.24) compared with those ≥20. There was no effect of participant treatment arm perception on risk behavior.

CONCLUSIONS

Our study of preexposure prophylaxis to prevent HIV infection found no evidence of risk compensation which may have been due to participants' motivations to reduce their risk behaviors and risk-reduction counseling.

Potential impact of pre-exposure prophylaxis for female sex workers and men who have sex with men in Bangalore, India: a mathematical modelling study

INTRODUCTION

In Bangalore, new HIV infections of female sex workers and men who have sex with men continue to occur, despite high condom use. Pre-exposure prophylaxis (PrEP) has high anti-HIV efficacy for men who have sex with men. PrEP demonstration projects are underway amongst Indian female sex workers. We estimated the impact and efficiency of prioritizing PrEP to female sex workers and/or men who have sex with men in Bangalore.

METHODS

A mathematical model of HIV transmission and treatment for female sex workers, clients, men who have sex with men and low-risk groups was parameterized and fitted to Bangalore data. The proportion of transmission attributable (population attributable fraction) to commercial sex and sex between men was calculated. PrEP impact (infections averted, life-years gained) and efficiency (life-years gained/infections averted per 100 person-years on PrEP) were estimated for different levels of PrEP adherence, coverage and prioritization strategies (female sex workers, high-risk men who have sex with men, both female sex workers and high-risk men who have sex with men, or female sex workers with lower condom use), under current conditions and in a scenario with lower baseline condom use amongst key populations.

RESULTS

Population attributable fractions for commercial sex and sex between men have declined over time, and they are predicted to account for 19% of all new infections between 2016 and 2025. PrEP could prevent a substantial proportion of infections amongst female sex workers and men who have sex with men in this setting (23%/27% over 5/10 years, with 60% coverage and 50% adherence), which could avert 2.9%/4.3% of infections over 5/10 years in the whole Bangalore population. Impact and efficiency in the whole population was greater if female sex workers were prioritized. Efficiency increased, but impact decreased, if only female sex workers with lower condom use were given PrEP. Greater impact and efficiency was predicted for the scenario with lower condom use.

CONCLUSIONS

PrEP could be beneficial for female sex workers and men who have sex with men in Bangalore, and give some benefits in the general population, especially in similar settings with lower condom use levels.

Choice in HIV testing: the acceptability and anticipated use of a self-administered at-home oral HIV test among South Africans

Combination HIV prevention is being widely promoted by funders. This strategy aims to offer HIV prevention choices that can be selected and combined to decrease HIV risk in ways that fit with each individual's situation. Treatment as prevention and pre-exposure prophylaxis are two new evidence-based strategies to decrease HIV incidence, both of which require high HIV testing rates to be effective, and the Joint United Nations Programme on HIV/AIDS (UNAIDS) has set a goal of 90% of HIV-positive individuals knowing their status by 2030. However, HIV testing rates in many countries remain suboptimal. Just as no single HIV prevention method is ideal for all people in all situations, no single HIV testing modality is likely to be acceptable to everyone. By offering HIV testing choices, we may be able to increase testing rates. However, many low-resourced countries have been slow to take up new HIV testing options such as the self-administered at-home oral HIV test that is currently available in the United States. In this paper, we present findings from 20 in-depth interviews, conducted in 2010, documenting opinions about self-administered at-home oral HIV testing, a testing modality still largely unavailable in Africa. Participants were clients of three primary healthcare clinics in South Africa. Self-testing was seen as enabling confidentiality/privacy, saving time, and facilitating testing together with partners. However, concerns were raised about psychological distress when testing at home without a counsellor. Some suggested this concern could be minimised by having experienced clinic-based HIV testing and counselling before getting self-testing kits for home use. Thus, self-administered HIV testing could be an option added to the current testing modalities to address some important barriers to testing.

Prospects for HIV control in South Africa: a model-based analysis

Background

The goal of virtual elimination of horizontal and mother-to-child HIV transmission in South Africa (SA) has been proposed, but there have been few systematic investigations of which interventions are likely to be most critical to reducing HIV incidence.

Objective

This study aims to evaluate SA's potential to achieve virtual elimination targets and to identify which interventions will be most critical to achieving HIV incidence reductions.

Design

A mathematical model was developed to simulate the population-level impact of different HIV interventions in SA. Probability distributions were specified to represent uncertainty around 32 epidemiological parameters that could be influenced by interventions, and correlation coefficients (r) were calculated to assess the sensitivity of the adult HIV incidence rates and mother-to-child transmission rates (2015–2035) to each epidemiological parameter.

Results

HIV incidence in SA adults (ages 15–49) is expected to decline from 1.4% in 2011–2012 to 0.29% by 2035 (95% CI: 0.10–0.62%). The parameters most strongly correlated with future adult HIV incidence are the rate of viral suppression after initiating antiretroviral treatment (ART) (r=−0.56), the level of condom use in non-marital relationships (r=−0.40), the phase-in of intensified risk-reduction counselling for HIV-positive adults (r=0.29), the uptake of medical male circumcision (r=−0.24) and the phase-in of universal ART eligibility (r=0.22). The paediatric HIV parameters most strongly associated with mother-to-child transmission rates are the relative risk of transmission through breastfeeding when the mother is receiving ART (r=0.70) and the rate of ART initiation during pregnancy (r=−0.16).

Conclusions

The virtual elimination target of a 0.1% incidence rate in adults will be difficult to achieve. Interventions that address the infectiousness of patients after ART initiation will be particularly critical to achieving long-term HIV incidence declines in South Africa.

Optimizing HIV prevention for women: a review of evidence from microbicide studies and considerations for gender-sensitive microbicide introduction

Introduction

Microbicides were conceptualized as a product that could give women increased agency over HIV prevention. However, gender-related norms and inequalities that place women and girls at risk of acquiring HIV are also likely to affect their ability to use microbicides. Understanding how gendered norms and inequalities may pose obstacles to women's microbicide use is important to inform product design, microbicide trial implementation and eventually microbicide and other antiretroviral-based prevention programmes. We reviewed published vaginal microbicide studies to identify gender-related factors that are likely to affect microbicide acceptability, access and adherence. We make recommendations on product design, trial implementation, positioning, marketing and delivery of microbicides in a way that takes into account the gender-related norms and inequalities identified in the review.

Methods

We conducted PubMed searches for microbicide studies published in journals between 2000 and 2013. Search terms included trial names (e.g. “MDP301”), microbicide product names (e.g. “BufferGel”), researchers’ names (e.g. “van der Straten”) and other relevant terms (e.g. “microbicide”). We included microbicide clinical trials; surrogate studies in which a vaginal gel, ring or diaphragm was used without an active ingredient; and hypothetical studies in which no product was used. Social and behavioural studies implemented in conjunction with clinical trials and surrogate studies were also included. Although we recognize the importance of rectal microbicides to women, we did not include studies of rectal microbicides, as most of them focused on men who have sex with men. Using a standardized review template, three reviewers read the articles and looked for gender-related findings in key domains (e.g. product acceptability, sexual pleasure, partner communication, microbicide access and adherence).

Results and discussion

The gendered norms, roles and relations that will likely affect women's ability to access and use microbicides are related to two broad categories: norms regulating women's and men's sexuality and power dynamics within intimate relationships. Though norms about women's and men's sexuality vary among cultural contexts, women's sexual behaviour and pleasure are typically less socially acceptable and more restricted than men's. These norms drive the need for woman-initiated HIV prevention, but also have implications for microbicide acceptability and how they are likely to be used by women of different ages and relationship types. Women's limited power to negotiate the circumstances of their intimate relationships and sex lives will impact their ability to access and use microbicides. Men's role in women's effective microbicide use can range from opposition to non-interference to active support.

Conclusions

Identifying an effective microbicide that women can use consistently is vital to the future of HIV prevention for women. Once such a microbicide is identified and licensed, positioning, marketing and delivering microbicides in a way that takes into account the gendered norms and inequalities we have identified would help maximize access and adherence. It also has the potential to improve communication about sexuality, strengthen relationships between women and men and increase women's agency over their bodies and their health.

Comparing the impact of increasing condom use or HIV pre-exposure prophylaxis (PrEP) use among female sex workers

In many settings, interventions targeting female sex workers (FSWs) could significantly reduce the overall transmission of HIV. To understand the role HIV pre-exposure prophylaxis (PrEP) could play in controlling HIV transmission amongst FSWs, it is important to understand how its impact compares with scaling-up condom use-one of the proven HIV prevention strategies for FSWs. It is important to remember that condoms also have other benefits such as reducing the incidence of sexually transmitted infections and preventing pregnancy. A dynamic deterministic model of HIV transmission amongst FSWs, their clients and other male partners (termed 'pimps') was used to compare the protection provided by PrEP for HIV-negative FSWs with FSWs increasing their condom use with clients and/or pimps. For different HIV prevalence scenarios, levels of pimp interaction, and baseline condom use, we estimated the coverage of PrEP that gives the same reduction in endemic FSW HIV prevalence or HIV infections averted as different increases in condom use. To achieve the same impact on FSW HIV prevalence as increasing condom use by 1%, the coverage of PrEP has to increase by >2%. The relative impact of PrEP increases for scenarios where pimps contribute to HIV transmission, but not greatly, and decreases with higher baseline condom use. In terms of HIV infections averted over 10 years, the relative impact of PrEP compared to condoms was reduced, with a >3% increase in PrEP coverage achieving the same impact as a 1% increase in condom use. Condom promotion interventions should remain the mainstay HIV prevention strategy for FSWs, with PrEP only being implemented once condom interventions have been maximised or to fill prevention gaps where condoms cannot be used.

Pre-exposure prophylaxis in Southern Africa: feasible or not?

INTRODUCTION

Southern and Eastern Africa bear the brunt of the AIDS epidemic, and current prevention interventions remain inadequate. Antiretroviral-based pre-exposure prophylaxis (PrEP) is gaining momentum as an effective prevention intervention.

DISCUSSION

Discussions have been started on how this strategy could be employed in Africa such that the populations most in need can be reached urgently for the greatest impact. This requires the selection of specific risk groups and service environments in which PrEP can be distributed safely and cost effectively while being mindful of any ethical issues.

CONCLUSIONS

Given the need for an integrated public health approach to this, a number of potential populations and opportunities for PrEP distribution exist and are discussed in this commentary.

The sheep as a model of preclinical safety and pharmacokinetic evaluations of candidate microbicides

When developing novel microbicide products for the prevention of HIV infection, the preclinical safety program must evaluate not only the active pharmaceutical ingredient but also the product itself. To that end, we applied several relatively standard toxicology study methodologies to female sheep, incorporating an assessment of the pharmacokinetics, safety, tolerability, and local toxicity of a dapivirine-containing human vaginal ring formulation (Dapivirine Vaginal Ring-004). We performed a 3-month general toxicology study, a preliminary pharmacokinetic study using drug-loaded vaginal gel, and a detailed assessment of the kinetics of dapivirine delivery to plasma, vaginal, and rectal fluid and rectal, vaginal, and cervical tissue over 28 days of exposure and 3 and 7 days after removal of the ring. The findings of the general toxicology study supported the existing data from both preclinical and clinical studies in that there were no signs of toxicity related to dapivirine. In addition, the presence of the physical dapivirine ring did not alter local or systemic toxicity or the pharmacokinetics of dapivirine. Pharmacokinetic studies indicated that the dapivirine ring produced significant vaginal tissue levels of dapivirine. However, no dapivirine was detected in cervical tissue samples using the methods described here. Plasma and vaginal fluid levels were lower than those in previous clinical studies, while there were detectable dapivirine levels in the rectal tissue and fluid. All tissue and fluid levels tailed off rapidly to undetectable levels following removal of the ring. The sheep represents a very useful model for the assessment of the safety and pharmacokinetics of microbicide drug delivery devices, such as the vaginal ring.

A systematic review of the psychometric properties of the Sexual Relationship Power Scale in HIV/AIDS research

The Sexual Relationship Power Scale (SRPS) was developed over a decade ago to address the lack of reliable and valid measures of relationship power in social, behavioral and medical research. The SRPS and its two subscales (relationship control [RC], decision-making dominance [DMD]) have been used extensively in the field of HIV prevention and sexual risk behavior. We performed a systematic review of the psychometric properties of the SRPS and subscales as reported in the HIV/AIDS literature from 2000 to 2012. A total of 54 published articles were identified, which reported reliability or construct validity estimates of the scales. Description of the psychometric properties of the SRPS and subscales is reported according to study population, and several cross-population trends were identified. In general, the SRPS and RC subscale exhibited sound psychometric properties across multiple study populations and research settings. By contrast, the DMD subscale had relatively weak psychometric properties, especially when used with specific populations and research settings. Factors that influenced the psychometric properties of the various scales and subscales included the study population, mean age of the sample, number of items retained in the scale, and modifications to the original scales. We conclude with recommendations for (1) the application and use of the SRPS and subscales, (2) reporting of psychometric properties of the scales in the literature, and (3) areas for future research.

Combination HIV prevention for female sex workers: what is the evidence?

Sex work occurs in many forms and sex workers of all genders have been affected by HIV epidemics worldwide. The determinants of HIV risk associated with sex work occur at several levels, including individual biological and behavioural, dyadic and network, and community and social environmental levels. Evidence indicates that effective HIV prevention packages for sex workers should include combinations of biomedical, behavioural, and structural interventions tailored to local contexts, and be led and implemented by sex worker communities. A model simulation based on the South African heterosexual epidemic suggests that condom promotion and distribution programmes in South Africa have already reduced HIV incidence in sex workers and their clients by more than 70%. Under optimistic model assumptions, oral pre-exposure prophylaxis together with test and treat programmes could further reduce HIV incidence in South African sex workers and their clients by up to 40% over a 10-year period. Combining these biomedical approaches with a prevention package, including behavioural and structural components as part of a community-driven approach, will help to reduce HIV infection in sex workers in different settings worldwide.

The development and validation of an UHPLC-MS/MS method for the rapid quantification of the antiretroviral agent dapivirine in human plasma

BACKGROUND

Dapivirine is a non-nucleoside reverse transcriptase inhibitor designed to prevent HIV-1 viral replication and subsequent propagation. A sensitive method is required to quantify plasma concentrations to assess drug efficacy.

RESULTS

Dapivirine-spiked plasma was combined with acetonitrile containing deuterated IS and was processed for analysis. The method has an analytical measuring range from 20 to 10,000 pg/ml. For the LLOQ, low, mid and high QCs, intra- and inter-assay precision (%CV) ranged from 5.58 to 13.89% and 5.23 to 13.36%, respectively, and intra- and inter-day accuracy (% deviation) ranged from -5.61 to 0.75% and -4.30 to 6.24%, respectively.

CONCLUSION

A robust and sensitive LC-MS/MS assay for the high-throughput quantification of the antiretroviral drug dapivirine in human plasma was developed and validated following bioanalytical validation guidelines. The assay meets criteria for the analysis of samples from large research trials.

Dynamic social support networks of younger black men who have sex with men with new HIV infection

Rising rates of HIV infection among younger black men who have sex with men (YBMSM) in the USA have generated a public health emergency. Living with HIV requires deep and persistent social support often available only from close confidants. Enlisting endogenous support network members into the care of HIV-infected YBMSM may help shape sustainable supportive environments, leading to long-term improvements in mental and HIV-specific health outcomes. The present study examined trends in support network change over time after new HIV diagnoses among 14 YBMSM. Participants completed a social network survey that utilized sociograms to record support confidants (SCs) preceding HIV diagnosis and at one and nine months postdiagnosis. Reported SCs included family of origin, friends, sex partners, and other associates. Analysis revealed three distinct patterns of change: high gain, high turnover, and stable networks. These patterns offer valuable insights into the social support of YBMSM during the period following diagnosis. This research underscores a growing movement to embrace key support figures in the lives of YBMSM, who may be critical to promoting overall health and adherence to HIV-care.

Cost-effectiveness of tenofovir gel in urban South Africa: model projections of HIV impact and threshold product prices

BACKGROUND

There is urgent need for effective HIV prevention methods that women can initiate. The CAPRISA 004 trial showed that a tenofovir-based vaginal microbicide had significant impact on HIV incidence among women. This study uses the trial findings to estimate the population-level impact of the gel on HIV and HSV-2 transmission, and price thresholds at which widespread product introduction would be as cost-effective as male circumcision in urban South Africa.

METHODS

The estimated 'per sex-act' HIV and HSV-2 efficacies were imputed from CAPRISA 004. A dynamic HIV/STI transmission model, parameterised and fitted to Gauteng (HIV prevalence of 16.9% in 2008), South Africa, was used to estimate the impact of gel use over 15 years. Uptake was assumed to increase linearly to 30% over 10 years, with gel use in 72% of sex-acts. Full economic programme and averted HIV treatment costs were modelled. Cost per DALY averted is estimated and a microbicide price that equalises its cost-effectiveness to that of male circumcision is estimated.

RESULTS

Using plausible assumptions about product introduction, we predict that tenofovir gel use could lead to a 12.5% and 4.9% reduction in HIV and HSV-2 incidence respectively, by year 15. Microbicide introduction is predicted to be highly cost-effective (under $300 per DALY averted), though the dose price would need to be just $0.12 to be equally cost-effective as male circumcision. A single dose or highly effective (83% HIV efficacy per sex-act) regimen would allow for more realistic threshold prices ($0.25 and $0.33 per dose, respectively).

CONCLUSIONS

These findings show that an effective coitally-dependent microbicide could reduce HIV incidence by 12.5% in this setting, if current condom use is maintained. For microbicides to be in the range of the most cost-effective HIV prevention interventions, product costs will need to decrease substantially.

Microbicides: topical prevention against HIV

Microbicides represent a potential intervention strategy for preventing HIV transmission. Vaginal microbicides would meet the need for a discreet method that women could use to protect themselves against HIV. Although early-generation microbicides failed to demonstrate efficacy, newer candidates are based on more potent antiretroviral (ARV) products. Positive data from the CAPRISA 004 trial of tenofovir gel support use in women and represent a turning point for the field. This article reviews current progress in development of ARV-based microbicides. We discuss the consensus on selection criteria, the potential for drug resistance, rationale for drug combinations, and the use of pharmacokinetic (PK)/pharmacodynamic (PD) assessment in product development. The urgent need for continued progress in development of formulations for sustained delivery is emphasized. Finally, as the boundaries between different prevention technologies become increasingly blurred, consideration is given to the potential synergy of diverse approaches across the prevention landscape.

Beating the placebo in HIV prevention efficacy trials: the role of the minimal efficacy bound

OBJECTIVES

To produce an effect on the HIV epidemic, preventive interventions need to achieve a minimum level of efficacy to offset potential indirect effects such as an increase in risky behavior. The current generation of HIV prevention trials on oral preexposure prophylaxis and on vaginal microbicides were designed using different set points for minimum individual-level efficacy (MIE). Some trials were designed not only to show superiority over placebo but also to rule out lower efficacies. The MIE has a substantial impact on the size and cost of a trial. Ideally, the MIE should be chosen to reduce uncertainty in the estimation of population-level effects. In this article, we investigate the effect of MIE on estimates of population-level impact to better inform trial design.

METHODS

We used mathematical model simulations assuming various rates of efficacy obtained from trials and different MIEs to study the impact of wide-scale interventions on 2 public health indicators.

RESULTS

Implementation factors were the main drivers of uncertainty in public health indicators for an intervention, although MIE also contributed. The level of uncertainty introduced by the MIE was substantially lower than that of the other factors.

CONCLUSIONS

Investigators in clinical trials have set the MIE solely on the basis of potential public health impact. However, the substantial increase in trial costs associated with a large MIE is unlikely to be justified. These additional funds would be better spent in evaluating more critical implementation factors that cannot be assessed in clinical trials.

Mathematical insights in evaluating state dependent effectiveness of HIV prevention interventions

Mathematical models have been used to simulate HIV transmission and to study the use of preexposure prophylaxis (PrEP) for HIV prevention. Often a single intervention outcome over 10 years has been used to evaluate the effectiveness of PrEP interventions. However, different metrics express a wide variation over time and often disagree in their forecast on the success of the intervention. We develop a deterministic mathematical model of HIV transmission and use it to evaluate the public-health impact of oral PrEP interventions. We study PrEP effectiveness with respect to different evaluation methods and analyze its dynamics over time. We compare four traditional indicators, based on cumulative number or fractions of infections prevented, on reduction in HIV prevalence or incidence and propose two additional methods, which estimate the burden of the epidemic to the public-health system. We investigate the short and long term behavior of these indicators and the effects of key parameters on the expected benefits from PrEP use. Our findings suggest that public-health officials considering adopting PrEP in HIV prevention programs can make better informed decisions by employing a set of complementing quantitative metrics.

Intravaginal practices and microbicide acceptability in Papua New Guinea: implications for HIV prevention in a moderate-prevalence setting

BACKGROUND

The acceptability of female-controlled biomedical prevention technologies has not been established in Papua New Guinea, the only country in the Pacific region experiencing a generalised, moderate-prevalence HIV epidemic. Socio-cultural factors likely to impact on future product uptake and effectiveness, such as women's ability to negotiate safer sexual choices, and intravaginal hygiene and menstrual practices (IVP), remain unclear in this setting.

METHODS

A mixed-method qualitative study was conducted among women and men attending a sexual health clinic in Port Moresby. During in-depth interviews, participants used copies of a hand-drawn template to indicate how they wash/clean the vulva and/or vagina. Interviewers pre-filled commercially available vaginal applicators with 2-3mL KY Jelly® to create a surrogate vaginal microbicide product, which was demonstrated to study participants.

RESULTS

A total of 28 IDIs were conducted (women=16; men=12). A diverse range of IVP were reported. The majority of women described washing the vulva only with soap and water as part of their daily routine; in preparation for sex; and following sexual intercourse. Several women described cleaning inside the vagina using fingers and soap at these same times. Others reported cleaning inside the vagina using a hose connected to a tap; using vaginal inserts, such as crushed garlic; customary menstrual 'steaming' practices; and the use of material fragments, cloth and newspaper to absorb menstrual blood. Unprotected sex during menstruation was common. The majority of both women and men said that they would use a vaginal microbicide gel for HIV/STI protection, should a safe and effective product become available. Microbicide use was considered most appropriate in 'high-risk' situations, such as sex with non-regular, transactional or commercial partners. Most women felt confident that they would be able to negotiate vaginal microbicide use with male sexual partners but if necessary would be prepared to use product covertly.

CONCLUSIONS

Notional acceptability of a vaginal microbicide gel for HIV/STI prevention was high among both women and men. IVP were diverse in nature, socio-cultural dimensions and motivators. These factors are likely to impact on the future acceptability and uptake of vaginal microbicides and other biomedical HIV prevention technologies in this setting.

Willingness of clinicians to integrate microbicides into HIV prevention practices in southern Africa

The first vaginal microbicide was recently proven effective in clinical trials. We assessed the willingness of clinicians to integrate microbicides into HIV prevention practices in Southern Africa, where women face elevated HIV risks. We conducted in-depth interviews (n = 60) and nationally representative surveys (n = 1,444) in South Africa and Zimbabwe with nurses and physicians. Over half of clinicians (58%) were aware of microbicides, with physicians far more likely than nurses to be familiar. Clinicians, including those in rural areas, were generally willing to discuss microbicides, a female-initiated method less effective than the condom, particularly when condom use was unlikely (70%). Fewer would include microbicides while counseling adolescents (51%). Most clinicians (85%) thought their patients would use microbicides; greater clinician familiarity with microbicides was significant for support. Training for both nurses and physicians prior to introduction is critical, so they have sufficient knowledge and skills to offer a microbicide upon availability.

The meaning of adherence when behavioral risk patterns vary: obscured use- and method-effectiveness in HIV-prevention trials

BACKGROUND

Recently promising trials of innovative biomedical approaches to prevent HIV transmission have been reported. Participants' non-adherence to the prevention methods complicates the analyses and interpretation of trial results. The influence of variable sexual behaviors within and between participants of trials further obscures matters. Current methodological and statistical approaches in HIV-prevention studies, as well as ongoing debates on contradictory trial results, may fail to accurately address these topics.

METHODOLOGY/PRINCIPAL FINDINGS

Through developing a cumulative probability model of infection within HIV prevention trials, we demonstrate how adherence and sexual behavior patterns impact the overall estimate of effectiveness, the effectiveness of prevention methods as a function of adherence, and conclusions about methods' true effectiveness. Applying the model to summary-level data from the CAPRISA trial, we observe markedly different values for the true method effectiveness of the microbicide, and show that if the gel would have been tested among women with slightly different sexual behavior patterns, conclusions might well have been that the gel is not effective.

CONCLUSIONS/SIGNIFICANCE

Relative risk and adherence analyses in HIV prevention trials overlook the complex interplay between adherence and sexual behavior patterns. Consequently, they may not provide accurate estimates of use- and method-effectiveness. Moreover, trial conclusions are contingent upon the predominant sexual behavior pattern of participants and cannot be directly generalized to other contexts. We recommend researchers to (re)examine their data and use the cumulative probability model to estimate the true method effectiveness, which might contribute to resolving current questions about contradictory trial results. Moreover, we suggest taking into account the issues raised in the design of future trials and in population models estimating the impact of large-scale dissemination of prevention methods. Comprehension of the topics described will help readers to better interpret (apparently contradictory) trial outcomes.

Condom migration resulting from circumcision, microbicides and vaccines: brief review and methodological considerations

OBJECTIVE

To provide an updated review of condom migration as a means of highlighting methodological issues for future studies of this behavioural issue.

METHODS

Electronic searches of PubMed, MEDLINE and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases were carried out in October 2010 and updated in January 2011 for English-language articles published from 1994 onward.

RESULTS

Evidence addressing condom migration from microbicides and vaccines is vastly underdeveloped, simply because these products are still experimental. In contrast, the more advanced evidence regarding male circumcision is hopeful because it suggests that migration may not be an overwhelming issue. Nonetheless, the entire body of empirical evidence on this question could be substantially expanded and improved.

CONCLUSION

Until stronger evidence suggests that condom migration is unlikely, it is important to be mindful of the potential for condom migration to occur in response to biomedical interventions (circumcision, microbicides and vaccines).

The "Swiss Statement": who knows about it? How do they know? What are its effects on people living with HIV/AIDS?

The publication of the "Swiss Statement" in 2008 shook the international HIV prevention and advocacy scene. HIV behavioral research has provided us with some studies focusing on the potential changes that new prevention strategies can produce, but results are not conclusive. Besides, there is a lack of data concerning awareness of these kinds of prevention strategies on real-life settings, studying mainly the behavior of people recruited in different types of trials (e.g., circumcision, pre and post-exposure prophylaxis). The present study aims to (1) identify the factors associated with awareness of the "Swiss Statement" among PLWHA, (2) determine in which setting they became aware of it, and (3) look for potential, behavioral, and/or emotional changes as a consequence of this awareness. In order to achieve these three objectives, we used the data collected by a community-based survey called "HIV, Hepatitis and you." In order to determine the factors associated with the awareness of the Swiss Statement, univariate and multivariate logistic regression were performed. Main results show that among the 997 HIV-positive people answering the questionnaire, 57% knew about the Swiss Statement, and that their main source of information was the associative setting, while 30% declared having found out about it from their doctor. As for the factors associated with the awareness of the Swiss Statement, we found that the following variables were significantly associated with such awareness: living in stable housing, having a CD4 count above 350 cell/mm(3), having an undetectable viral load, being in contact with a HIV-solidarity network, feeling of belonging to the LGBT community, and filling out the questionnaire online. The results of this study point out that interventions addressed to improve access to health-related information for PLWHA facing socioeconomical difficulties and isolation are strongly needed.

Preventive misconception as a motivation for participation and adherence in microbicide trials: evidence from female participants and male partners in Malawi and Zimbabwe

This paper presents empirical data on motivation to join an HIV prevention trial of vaginal microbicide gels in Malawi and Zimbabwe, and participant assumption of a preventive misconception. Interviews were conducted with women participating in the trial and their male partners. Most of the female participants were able to adequately describe basic aspects of the trial design. HIV counseling and testing were primary reasons motivating women's participation, and male partners' support of the trial. 29% of women and 20% of men also provided indications of a preventive misconception, attributing gel use and trial participation to avoiding HIV infection.

Preclinical evaluation of the HIV-1 fusion inhibitor L'644 as a potential candidate microbicide

Topical blockade of the gp41 fusogenic protein of HIV-1 is one possible strategy by which microbicides could prevent HIV transmission, working early against infection, by inhibiting viral entry into host cells. In this study, we examined the potential of gp41 fusion inhibitors (FIs) as candidate anti-HIV microbicides. Preclinical evaluation of four FIs, C34, T20, T1249, and L'644, was performed using cellular and ex vivo genital and colorectal tissue explant models. Increased and sustained activity was detected for L'644, a cholesterol-derivatized version of C34, relative to the other FIs. The higher potency of L'644 was further increased with sustained exposure of cells or tissue to the compound. The activity of L'644 was not affected by biological fluids, and the compound was still active when tissue explants were treated after viral exposure. L'644 was also more active than other FIs against a viral escape mutant resistant to reverse transcriptase inhibitors (RTIs), demonstrating the potential of L'644 to be included as part of a multiactive antiretroviral (ARV) combination-based microbicide. These data support the further development of L'644 for microbicide application.

A qualitative study of obstacles to diaphragm and condom use in an HIV prevention trial in sub-Saharan Africa

Consistent condom use and the substitution of condoms with potential HIV prevention methods of lower or unknown effectiveness are important concerns in the development of new prevention technologies. This qualitative study explored obstacles to consistent condom use with the diaphragm in MIRA, an HIV prevention trial in South Africa and Zimbabwe. We conducted 26 focus group discussions (FGDs) with 206 women and 7 FGDs and 10 in-depth interviews with 41 male partners of intervention-arm women. The belief that the diaphragm/gel prevented HIV, women's difficulties negotiating condom use, and men's unawareness that using the products together was recommended were obstacles to consistent condom use with the diaphragm/gel. Concerns about protection from HIV and pregnancy, recognition that the diaphragm was not yet proven to prevent HIV or sexually transmitted infections, and the trial context were facilitators. Understanding selective study product use in HIV prevention trials may inform improved adherence counseling and male involvement strategies.

Zinc acetate/carrageenan gels exhibit potent activity in vivo against high-dose herpes simplex virus 2 vaginal and rectal challenge

Topical microbicides that block the sexual transmission of HIV and herpes simplex virus 2 (HSV-2) are desperately needed to reduce the incidence of HIV infections worldwide. Previously we completed phase 3 testing of the carrageenan-based gel Carraguard. Although the trial did not show that Carraguard is effective in preventing HIV transmission during vaginal sex, it did show that Carraguard is safe when used weekly for up to 2 years. Moreover, Carraguard has in vitro activity against human papillomavirus (HPV) and HSV-2 and favorable physical and rheological properties, which makes it a useful vehicle to deliver antiviral agents such as zinc acetate. To that end, we previously reported that a prototype zinc acetate carrageenan gel protects macaques against vaginal challenge with combined simian-human immunodeficiency virus reverse transcriptase (SHIV-RT). Herein, we report the safety and efficacy of a series of zinc acetate and/or carrageenan gels. The gels protected mice (75 to 85% survival; P < 0.001) against high-dose (10(6)-PFU) HSV-2 vaginal or rectal challenge. In contrast, zinc acetate formulated in HEC (hydroxyethylcellulose; or the Universal Placebo) failed to protect mice against the high-dose vaginal HSV-2 challenge (similar to aqueous zinc acetate solution and the placebo controls). The gels were found to be effective spreading gels, exhibited limited toxicity in vitro, caused minimal damage to the architecture of the cervicovaginal and rectal mucosae in vivo, and induced no increased susceptibility to HSV-2 infection in a mouse model. Our results provide a strong rationale to further optimize and evaluate the zinc acetate/carrageenan gels for their ability to block the sexual transmission of HIV and HSV-2.

HIV treatment as prevention: principles of good HIV epidemiology modelling for public health decision-making in all modes of prevention and evaluation

Public health responses to HIV epidemics have long relied on epidemiological modelling analyses to help prospectively project and retrospectively estimate the impact, cost-effectiveness, affordability, and investment returns of interventions, and to help plan the design of evaluations. But translating model output into policy decisions and implementation on the ground is challenged by the differences in background and expectations of modellers and decision-makers. As part of the PLoS Medicine Collection "Investigating the Impact of Treatment on New HIV Infections"--which focuses on the contribution of modelling to current issues in HIV prevention--we present here principles of "best practice" for the construction, reporting, and interpretation of HIV epidemiological models for public health decision-making on all aspects of HIV. Aimed at both those who conduct modelling research and those who use modelling results, we hope that the principles described here will become a shared resource that facilitates constructive discussions about the policy implications that emerge from HIV epidemiology modelling results, and that promotes joint understanding between modellers and decision-makers about when modelling is useful as a tool in quantifying HIV epidemiological outcomes and improving prevention programming.

The future role of rectal and vaginal microbicides to prevent HIV infection in heterosexual populations: implications for product development and prevention

OBJECTIVES

To compare the potential impact of rectal (RMB), vaginal (VMB) and bi-compartment (RVMB) (applied vaginally and protective during vaginal and anal intercourse) microbicides to prevent HIV in various heterosexual populations. To understand when a RMB is as useful than a VMB for women practicing anal intercourse (AI).

METHODS

Mathematical model was used to assess the population-level impact (cumulative fraction of new HIV infections prevented (CFP)) of the three different microbicides in various intervention scenarios and prevalence settings. We derived the break-even RMB efficacy required to reduce a female's cumulative risk of HIV infection by the same amount than a VMB.

RESULTS

Under optimistic coverage (fast roll-out, 100% uptake), a 50% efficacious VMB used in 75% of sex acts in population without AI may prevent ∼33% (27, 42%) new total (men and women combined) HIV infections over 25 years. The 25-year CFP reduces to ∼25% (20, 32%) and 17% (13, 23%) if uptake decreases to 75% and 50%, respectively. Similar loss of impact (by 25%-50%) is observed if the same VMB is introduced in populations with 5%-10% AI and for RR(RAI)=4-20. A RMB is as useful as a VMB (ie, break-even) in populations with 5% AI if RR(RAI)=20 and in populations with 15%-20% AI if RR(RAI)=4, independently of adherence as long as it is the same with both products. The 10-year CFP with a RVMB is twofold larger than for a VMB or RMB when AI=10% and RR(RAI)=10.

CONCLUSIONS

Even low AI frequency can compromise the impact of VMB interventions. RMB and RVMB will be important prevention tools for heterosexual populations.

Moving beyond safe sex to women-controlled safe sex: a concept analysis

AIM

This paper is a report of a conceptual analysis of women-controlled safe sex.

BACKGROUND

Women bear disproportionate burdens from sexually related health compromising outcomes. Imbalanced societal gender and power positions contribute to high morbidities. The expression, women-controlled safe sex, aims to empower women to gain control of their sexual lives. Few researchers focus on contextualized socio-cultural definitions of sexual safety among women.

DATA SOURCES

The sample included scientific literature from Scopus, CINAHL, PubMed, PsychINFO and Sociological Abstracts. Papers were published 2000-2010.

REVIEW METHODS

Critical analyses of literature about women-controlled safe sex were performed in May 2011 using Rodgers' evolutionary concept analysis methods. The search focused on social and cultural influences on sexual practices aimed at increasing women's control over their sexual safety.

RESULTS

The analysis uncovered five attributes of women-controlled safe sex: technology; access to choices; women at-risk; 'condom migration' panic; and communication. Three antecedents included: male partner influence; body awareness; and self-efficacy. Consequences were categorized as positive or negative. Nine surrogate terms included: empowerment; gender power; female-controlled sexual barrier method; microbicides; diaphragm; sexual negotiation and communication; female condom; women-initiated disease transmission prevention; and spermicides. Finally, a consensus definition was identified: a socio-culturally influenced multi-level process for initiating sexual safety by women deemed at-risk for sexually related dangers, usually sexually transmitted infections and/or HIV/AIDS.

CONCLUSION

This concept analysis described current significance, uses, and applications of women-controlled safe sex in the scientific literature. The authors clarified its limited nature and conclude that additional conceptual refinement in nursing is necessary to influence women's health.

'The study has taught me to be supportive of her': empowering women and involving men in microbicide research

Recognising that women often have little control over most HIV-prevention methods, including condoms, researchers have made efforts to develop new bio-technological interventions, such as microbicides, that could allow women greater autonomy in HIV-prevention decision making. In many situations, women are unable to negotiate condom use with their partners, meaning that they could be better protected through the use of an effective microbicide. This paper uses qualitative data from the Microbicide Development Programme 301 (MDP301) microbicide trial in Johannesburg, South Africa. Data is taken from in-depth interviews with male partners of female trial participants (n = 28), six focus-group discussions involving male partners of trial participants (n = 4) and female participants (n = 2). Data show that men's involvement in microbicide research ranges from a disinterest in trials to the desire to actively take part in and promote research that affects the health of themselves and their partners. Results showed that some participants were reluctant to disclose trial involvement and product use to their partners, making identifying men as potential research participants problematic. This paper considers how to involve men in microbicide research without undermining women's sense of empowerment and ownership of the trial and the product that is being tested.

Modeling the gender-specific impact of vaginal microbicides on HIV transmission

Vaginal microbicides (VMB) are currently among the few women-initiated biomedical interventions for preventing heterosexual transmission of HIV. In this paper we use a deterministic model of HIV transmission to assess the public-health benefits of a VMB intervention and evaluate its gender-specific impact over short (initial) and extended periods of time. We define two distinct quantitative benefit ratios (QBRs) based on infections prevented in men and women to create and study regions of male advantage in different parameter spaces. Our analysis exposes complicated temporal correlations between the QBRs and series of pre-intervention (e.g., HIV acquisition risks per act) and intervention parameters (e.g., VMB efficacy mechanisms, rates of resistance development and reversion) and indicates that different QBRs may often disagree on the gender distribution of the benefits from a VMB intervention. We also outline the strong influence of some modeling assumptions on the reported results and conclude that the assessment of VMB and other biomedical interventions must be based on more comprehensive analyses than calculations of infections prevented over a fixed period of time.

Do women using long-acting reversible contraception reduce condom use? A novel study design incorporating semen biomarkers

Long-acting reversible contraceptive (LARC) methods are highly effective against pregnancy. A barrier to their widespread promotion can include the concern they will lead reduced condom use and, thus, will put couples at higher risk for sexually transmitted infections (STIs). We review evidence from previous studies of condom "migration" associated with the use of LARC and propose a novel study design to address the two main methodological issues that have limited these earlier studies. Namely, we propose to use a randomized controlled trial design and to use a biological marker of semen exposure for measuring changes in condom use.

Uptake of biomedical interventions for prevention of sexually transmitted HIV

PURPOSE OF THE REVIEW

To examine the population-level effects of introducing and/or expanding biomedical interventions for prevention of human immunodeficiency virus (HIV) sexually transmitted infections through mathematical modeling.

RECENT FINDINGS

Successes of several ground-breaking clinical trials have invigorated the field of HIV prevention with new enthusiasm and opportunities for research into and application of biomedical HIV prevention. Mathematical modeling has advanced in tandem with valuable contributions to both investigative science and public health. New models provide qualitative and quantitative insights regarding the epidemiological impact of the uptake of biomedical interventions, singly and/or in combination including treatment of sexually transmitted infections, condom use, male circumcision, antiretroviral treatment and pre-exposure prophylaxis and vaccine for HIV prevention.

SUMMARY

Biomedical interventions are critical for reversing the HIV pandemic. Mathematical modeling is invaluable for informed biomedical HIV prevention research, policy and practice.

Topical microbicides to prevent the transmission of HIV: formulation gaps and challenges

The efforts of the topical microbicide field to identify a safe and effective topical microbicide were realized in July of 2010 with the reporting of the results of the Centre for the AIDS Programme of Research in South Africa 004 trial. In this trial, a 1% tenofovir gel was found to reduce women's risk for HIV acquisition by 39% compared to placebo. To understand the impact of this trial on future microbicide development, we must view it from the historical perspective of previous phases 2 and 3 clinical trials with detergents and sulfated polyanions. This knowledge and emerging information must then be parlayed into the next steps needed to create a safe, effective, and acceptable topical microbicide. This review will look at the lessons learned from preclinical and clinical development of topical microbicides, focusing on two significant future challenges: (1) topical microbicide formulation safety and (2) the critical role that adherence to product use has in determining safety and efficacy in clinical trials and ultimately commercial viability of the licensed product. In addition to framing these issues within our current understanding of formulation and prevention of HIV acquisition, recent advances in our understanding of the mechanism of HIV transmission and how it informs on future formulation strategies will be briefly discussed.

An antiretroviral/zinc combination gel provides 24 hours of complete protection against vaginal SHIV infection in macaques

BACKGROUND

Repeated use, coitus-independent microbicide gels that do not contain antiretroviral agents also used as first line HIV therapy are urgently needed to curb HIV spread. Current formulations require high doses (millimolar range) of antiretroviral drugs and typically only provide short-term protection in macaques. We used the macaque model to test the efficacy of a novel combination microbicide gel containing zinc acetate and micromolar doses of the novel non-nucleoside reverse transcriptase inhibitor MIV-150 for up to 24 h after repeated gel application.

METHODS AND FINDINGS

Rhesus macaques were vaginally challenged with SHIV-RT up to 24 h after repeated administration of microbicide versus placebo gels. Infection status was determined by measuring virologic and immunologic parameters. Combination microbicide gels containing 14 mM zinc acetate dihydrate and 50 µM MIV-150 afforded full protection (21 of 21 animals) for up to 24 h after 2 weeks of daily application. Partial protection was achieved with the MIV-150 gel (56% of control at 8 h after last application, 11% at 24 h), while the zinc acetate gel afforded more pronounced protection (67% at 8-24 h). Marked protection persisted when the zinc acetate or MIV-150/zinc acetate gels were applied every other day for 4 weeks prior to challenge 24 h after the last gel was administered (11 of 14 protected). More MIV-150 was associated with cervical tissue 8 h after daily dosing of MIV-150/zinc acetate versus MIV-150, while comparable MIV-150 levels were associated with vaginal tissues and at 24 h.

CONCLUSIONS

A combination MIV-150/zinc acetate gel and a zinc acetate gel provide significant protection against SHIV-RT infection for up to 24 h. This represents a novel advancement, identifying microbicides that do not contain anti-viral agents used to treat HIV infection and which can be used repeatedly and independently of coitus, and underscores the need for future clinical testing of their safety and ability to prevent HIV transmission in humans.

Should microbicides be controlled by women or by physicians?

In 2007, nearly 7000 new cases of HIV infection occurred each day. There is a constant increase in the proportion of women newly infected with HIV in the global population; this increase is particularly high in some areas of the world such as sub-Saharan Africa. Microbicides are products that are being developed to empower women against HIV. First- and second-generation microbicides are broad-spectrum products that include surface active agents, vaginal defense enhancers, and blocking agents. Third-generation microbicides are HIV-specific and include replication and entry inhibitors formulated as gels or as vaginal rings. However, there is a concern that antiretroviral-based microbicides could lead to drug resistance if they are used by HIV-positive women who are unaware of their HIV status. To reach the highest number of women possible, microbicides should be available over-the-counter, which might not be the case with antiretroviral-based formulations. In contrast, non-antiretroviral-based microbicides will have the advantage of being initiated and controlled by women themselves and they will not jeopardize the use of life-saving drugs.

Assessment of changes in condom use among female sex workers in a prospective cohort study introducing diaphragm use for disease prevention

Changes in the rates of condom use and number of sexual partners were evaluated among 140 female sex workers in Kibera, Kenya, participating in a 6-month study of diaphragm safety and acceptability for prevention of sexually transmitted infections conducted in 2004-2005. Analyses were stratified by partner type. Multivariable Tobit regression modeling was used to assess the association between study visit and proportion of acts protected. Participants completed 140 baseline visits and 390 bimonthly follow-up visits. The mean percentage of coital acts reported as protected by a condom increased from 56% at baseline to 68% at the 6-month visit (P < 0.01). Similar increases were observed for condom use by all partner types. Additionally, the mean number of sexual partners decreased over the study. Furthermore, consistent (i.e., 100%) diaphragm use during follow-up was associated with a higher proportion of coital acts protected by a condom in analyses adjusted for study visit and coital frequency. These findings suggest that, despite concerns that introduction of the diaphragm would result in more risky sexual behaviors, reported condom use increased and number of partners decreased.

Apples and oranges? Interpreting success in HIV prevention trials

BACKGROUND

In the last decade, several large-scale, clinical trials evaluating the efficacy of novel HIV prevention products have been completed, and eight are currently underway or about to be reported. Little attention has been given in the literature to the level of protection sufficient to warrant introduction, and there is concern that using the term "efficacy" to describe the effect of user-controlled methods such as microbicides may mislead policymakers.

DESIGN

We review how the fields of family planning, vaccine science and mathematical modelling understand and use the terms efficacy and effectiveness, and explore with simple mathematical models how trial results of user-controlled products relate to common understandings of these terms.

RESULTS

Each field brings different assumptions, a different evidence base and different expectations to interpretations of efficacy and effectiveness - a reality that could cloud informed assessment of emerging data.

CONCLUSION

When making judgments on the utility of new health technologies, it is important to use standards that yield appropriate comparisons for the innovation and that take into account the local epidemic and available alternatives.

Potential impact of vaginal microbicides on HIV risk among women with primary heterosexual partners

This article explores the potential public health consequences of anti-HIV microbicide adoption among women in high-risk communities, using data from an exploratory study to illustrate key points. A brief quantitative survey was administered to 71 drug-using women with primary heterosexual partners in New York City. Only 37% of women reported recent condom use with a primary male partner. A total of 86% expressed willingness to use a microbicide with a primary partner. Among women using condoms, 50% believed they would decrease condom use if they started using a vaginal microbicide. Although overall condom use and intended condom migration was low among women with HIV-infected partners, universal promotion of microbicides could nonetheless lead to an increase in HIV risk among specific subgroups of women, indicating the importance of promoting continued condom use. Further research is needed to inform public policy decisions before the availability of the first commercial microbicide.