On-Demand Preexposure Prophylaxis in Men at High Risk for HIV-1 Infection

Evolution of Risk Behaviors, Sexually Transmitted Infections and PrEP Care Continuum in a Hospital-Based PrEP Program in Barcelona, Spain: A Descriptive Study of the First 2 Years' Experience

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is effective for HIV prevention, but the PrEP care continuum also involves improving PrEP awareness, uptake, adherence, and retention in care. Users' awareness is often compromised because of vulnerability factors and risk behaviors, such as chemsex practice or specific substance use, which could lead to risk compensation. Correct adherence and retention in care are essential to achieve the full effectiveness of PrEP. This study describes changes in users' risk behaviors and sexually transmitted infections (STIs), as well also PrEP care continuum details.

METHODS

This was a descriptive single-center retrospective study including adults at high HIV risk screened between November 2019 and June 2021 in the PrEP program of our hospital. Demographic, behavioral, STI, adherence, and retention in care variables were assessed. Data were collected from medical records and self-report questionnaires.

RESULTS

A total of 295 people were included, 94% men and 5% transgender women, with a mean age of 34 years (SD 10) and 10% sex workers. At baseline, 55% disclosed chemsex practice and 3% slamming. During follow-up, condom use for anal intercourse decreased from 41% to 13% (p ≤ 0.0001) and one HIV infection was detected; other risk behaviors and STIs remained stable. Chemsex, group sex, fluid exchange, and condomless anal intercourse were related to STI risk. Adherence was correct in 80% of users, and retention in care was 57%. Discontinuations and loss to follow-up were high, mainly affecting transgender women, sex workers, and people practicing fisting.

CONCLUSION

PrEP program implementation in our hospital was adequate, since it allowed, in a population at high HIV risk, overall users' risk behaviors and STIs to remain stable, with only one HIV diagnosis during the follow-up. We should target specific strategies to improve adherence and retention in care, as vulnerable subgroups at higher risk of loss to follow-up are identified.

Cabotegravir-Global Access to Long-Acting Pre-exposure Prophylaxis for HIV

A novel injectable pre-exposure prophylaxis, cabotegravir, has greater efficacy and acceptability than oral tenofovir/emtricitabine for prevention of HIV infection. Cabotegravir is currently priced at $22 200 per year, >185 times higher than the $60-$119 estimated cost-effectiveness threshold for middle-income countries (MICs). Following civil society pressure, ViiV provided access to generic versions in 90 countries with the Medicines Patent Pool (MPP), including all African nations. However, several MICs outside Africa have rapidly growing HIV epidemics. We analyzed the ViiV-MPP deal to assess population covered and gross domestic product (GDP) per capita. There were 38 countries excluded from the ViiV-MPP deal despite having a GDP per capita lower than the highest-earning African country. These countries include 2.4 billion people (30% global population), with an incidence of 122 000 (8%). For cabotegravir to have a significant impact on HIV infections, millions will need to be treated at affordable prices in a wide range of countries.

Hypo-osmolar rectal douche tenofovir formulation prevents simian/human immunodeficiency virus acquisition in macaques

In spite of the rollout of oral pre-exposure prophylaxis (PrEP), the rate of new HIV infections remains a major health crisis. In the United States, new infections occur predominantly in men having sex with men (MSM) in rural settings where access to PrEP can be limited. As an alternative congruent with MSM sexual behavior, we have optimized and tested tenofovir (TFV) and analog-based iso-osmolar and hypo-osmolar (HOsm) rectal douches for efficacy against rectal simian/human immunodeficiency virus (SHIV) infection of macaques. Single TFV HOsm high-dose douches achieved peak plasma TFV levels similar to daily oral PrEP, while other formulations yielded lower concentrations. Rectal tissue TFV-diphosphate (TFV-DP) concentrations at the portal of virus entry, however, were markedly higher after HOsm douching than daily oral PrEP. Repeated douches led to significantly higher plasma TFV and higher TFV-DP concentrations in rectal tissue at 24 hours compared with single douches, without detectable mucosal or systemic toxicity. Using stringent repeated intrarectal SHIV exposures, single HOsm high-dose douches delivered greater protection from virus acquisition for more than 24 hours compared with oral PrEP. Our results demonstrate a rapid delivery of protective TFV doses to the rectal portal of virus entry as a potential low-cost and safe PrEP alternative.

Long-acting injectable cabotegravir for PrEP: A game-changer in HIV prevention?

BACKGROUND

Long-acting injectable cabotegravir (CAB-LA) represents a new additional option for HIV prevention in people at substantial risk of HIV infection that may fill the gaps in pre-exposure prophylaxis (PrEP) uptake, adherence, and retention in users having difficulty with oral PrEP. Data from clinical trials demonstrated that CAB-LA was safe, highly effective, and well-accepted for HIV prevention. However, the occurrence of breakthrough HIV infections despite timely injections, HIV seroconversion timing and patterns, risk of selection and dissemination of resistance-associated mutations to integrase inhibitors, complexity of follow-up, logistical considerations, and its cost effectiveness compared with oral PrEP constitute significant issues for the integration of CAB-LA into clinical routine.

FINDINGS

These concerns need to be addressed before moving forward with large-scale implementation programmes. Pilot and implementation projects are required in the following areas: HIV testing algorithms, patient education, clinic procedures, protocols for switching and discontinuation, efficacy and safety in populations not included in clinical trials, and demedicalization processes. The development of models to increase the uptake of, adherence to, and persistence with and after CAB-LA injections will also be of paramount importance for success. Lessons learned from these projects will increase experience, staff expertise, and organizational and training capacities to support the roll-out of this new agent as part of HIV prevention programmes.

CONCLUSION

CAB-LA has not yet achieved its full potential in HIV prevention, and strong commitment from all stakeholders is required to push CAB-LA as a game-changer in HIV response.

Pre-exposure prophylaxis in France: How many MSM are eligible and how much will it cost?

BACKGROUND

Pre-exposure prophylaxis (PrEP) was definitively authorized in France in 2017 after a two-year probationary period. The fact that the estimated number of MSM eligible for PrEP is still unknown is a barrier to this prevention tool's roll-out at the national level. This study aimed to estimate the number of MSM eligible for PrEP in France, and to evaluate the direct cost of its roll-out.

METHODS

We used data from several sources including the Enquête Rapport au Sexe 2019-ERAS 2019 survey, the 2019 French population census from National Institute of Statistics and Economic Studies (INSEE), and the National Public Health Agency's (Santé Publique France) 2016 health barometer survey. We also used data from previous studies which estimated the proportion of MSM who were sexually active in the 12 months prior to the studies, and HIV prevalence in MSM in France. Furthermore, we used data on PrEP drug costs from the French public drug database and data on medical examinations costs from the IPERGAY study.

RESULTS

For 2019, the number of HIV seronegative MSM in France who were sexually active in the previous 12 months was estimated at 398,015. Of these, 142,379 (95%CI: 139,893-145,241) and 104,645 (95%IC: 102311-106979) were eligible for PrEP, based on the Menza score and on official French criteria, respectively. The overall estimated cost of PrEP roll-out in eligible MSM varied between € 317,685,216 and € 545,903,216 for official French criteria, which was higher than the estimated €432,240,851 and €742,753,074 according to the Menza score.

CONCLUSIONS

Our estimations will enable policy makers to make evidence-based decisions about PrEP roll-out to MSM in France. To accelerate the process, it is important to decentralize PrEP delivery, authorize general practitioners to write prescriptions, and promote this prevention tool through information campaigns.

Single dose topical inserts containing tenofovir alafenamide fumarate and elvitegravir provide pre- and post-exposure protection against vaginal SHIV infection in macaques

BACKGROUND

Vaginal products for HIV prevention that can be used on-demand before or after sex may be a preferable option for women with low frequency or unplanned sexual activity or who prefer not to use daily or long-acting pre-exposure prophylaxis (PrEP). We performed dose ranging pharmacokinetics (PK) and efficacy studies of a vaginally applied insert containing tenofovir alafenamide fumarate (TAF) and elvitegravir (EVG) in macaques under PrEP or post-exposure prophylaxis (PEP) modalities.

METHODS

PK studies were performed in 3 groups of pigtailed macaques receiving inserts with different fixed-dose combinations of TAF and EVG (10/8, 20/16 and 40/24 mg). PrEP and PEP efficacy of a selected insert was investigated in a repeat exposure vaginal SHIV transmission model. Inserts were administered 4 h before (n = 6) or after (n = 6) repeated weekly SHIV exposures. Infection outcome was compared with macaques receiving placebo inserts (n = 12).

FINDINGS

Dose ranging studies showed rapid and sustained high drug concentrations in vaginal fluids and tissues across insert formulations with minimal dose proportionality. TAF/EVG (20/16 mg) inserts were selected for efficacy evaluation. Five of the 6 animals receiving these inserts 4 h before and 6/6 animals receiving inserts 4 h after SHIV exposure were protected after 13 challenges (p = 0.0088 and 0.0077 compared to placebo, respectively). The calculated PrEP and PEP efficacy was 91.0% (95% CI = 32.2%-98.8%) and 100% (95% CI = undefined), respectively.

INTERPRETATION

Inserts containing TAF/EVG provided high protection against vaginal SHIV infection when administered within a 4 h window before or after SHIV exposure. Our results support the clinical development of TAF/EVG inserts for on-demand PrEP and PEP in women.

FUNDING

Funded by CDC intramural funds, an interagency agreement between CDC and USAID (USAID/CDC IAA AID-GH-T-15-00002), and by the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) through the U.S. Agency for International Development (USAID) under a Cooperative Agreement (AID-OAA-A-14-00010) with CONRAD/Eastern Virginia Medical School.

Sexual behavior and medication adherence in men who have sex with men participating in a pre-exposure prophylaxis study of combinations of Maraviroc, Tenofovir Disoproxil Fumarate and/or Emtricitabine (HPTN 069/ACTG 5305)

HPTN 069/ACTG 5305 was designed to evaluate potential new PrEP regimens that included maraviroc, tenofovir disoproxil fumarate, and/or emtricitabine. The current analyses assessed antiretroviral (ARV) plasma concentrations in relation to sexual behavior in 224 cisgender men who have sex with men and 2 transgender women at risk for HIV. Poisson generalized estimating equations (GEE) regression were used to test for associations between self-reported sexual behavior, sociodemographic, behavioral variables, and study drug levels The median (IQR) age was 30 [25, 37] years old; 48.2% had completed college; 27.4% were Black and 21.7% Latino. At weeks 24 and 48, one third of participants reported condomless anal sex (CAS) in the prior month with more than one partner. CAS was associated with daily ARV drug use (χ2 = 12.64, p = 0.002). Older individuals and those with greater education were more likely to ingest ARV drugs daily (χ2 = 9.36, p = 0.009 and χ2 = 8.63, p = 0.013, respectively), while neither race nor ethnicity was associated with daily ARV drug use. Participants who reported recent condomless anal sex and/or advanced education had higher rates of daily ARV drug use. These data support the need for ongoing adherence counseling in clinical trials of new PrEP modalities.

Free HIV self-test for identification and linkage to care of previously undetected HIV infection in men who have sex with men in England and Wales (SELPHI): an open-label, internet-based, randomised controlled trial

BACKGROUND

High levels of HIV testing in men who have sex with men remain key to reducing the incidence of HIV. We aimed to assess whether the offer of a single, free HIV self-testing kit led to increased HIV diagnoses with linkage to care.

METHODS

SELPHI was an internet-based, open-label, randomised controlled trial that recruited participants via sexual and social networking sites. Eligibility criteria included being a man or trans woman (although trans women are reported separately); being resident in England or Wales, UK; being aged 16 years or older; having had anal intercourse with a man; not having a positive HIV diagnosis; and being willing to provide name, email address, date of birth, and consent to link to national HIV databases. Participants were randomly allocated (3:2) by computer-generated number sequence to receive a free HIV self-test kit (BT group) or to not receive this free kit (nBT group). Online surveys collected data at baseline, 2 weeks after enrolment (BT group only), 3 months after enrolment, and at the end of the study. The primary outcome was confirmed (linked to care) new HIV diagnosis within 3 months of enrolment, analysed by intention to treat. Those assessing the primary outcome were masked to allocation. This study is registered with the ISRCTN Clinical Trials Register, number ISRCTN20312003.

FINDINGS

10 111 participants (6049 in BT group and 4062 in nBT group) enrolled between Feb 16, 2017, and March 1, 2018. The median age of participants was 33 years (IQR 26-44 years); 9000 (89%) participants were White; 8118 (80%) participants were born in the UK; 81 (1%) participants were transgender men; 4706 (47%) participants were university educated; 1537 (15%) participants had never been tested for HIV; and 389 (4%) participants were taking pre-exposure prophylaxis. At enrolment, 7282 (72%) participants reported condomless anal sex with at least one male partner in the previous 3 months. In the BT group, of the 4511 participants for whom HIV testing information was available, 4263 (95%) reported having used the free HIV self-test kit within 3 months.Within 3 months of enrolment there were 19 confirmed new HIV diagnoses (0·31%) in 6049 participants in the BT group and 15 (0·37%) of 4062 in the nBT group (p=0·64).

INTERPRETATION

The offer of a single, free HIV self-test did not lead to increased rates of new HIV diagnoses, which could reflect decreasing HIV incidence rates in the UK. Nonetheless, the offer of a free HIV self-testing kit resulted in high HIV testing rates, indicating that self-testing is an attractive testing option for a large group of men who have sex with men.

FUNDING

UK National Institute for Health and Care Research.

Chemsex Practices in PrEP: Beyond Addiction and Risk Toward a Healthy Sex Life-Baseline Experiences from a Hospital-Based PrEP Program in Barcelona, Spain

Pre-exposure prophylaxis (PrEP) is a biomedical intervention that has demonstrated efficacy in HIV prevention in individuals at high-risk, among them chemsex users. Out of 190 PrEP users followed at Hospital Clinic of Barcelona until October 2020, 89% reported drug use, and 63% disclosed that they had engaged in chemsex practices, initiated in 64% of cases within the past year. Twenty-one percent used 3 or more drugs simultaneously, being GHB/GBL, nitrites, sildenafil, and methamphetamine the most prevalent combination. Eight percent reported slamming. Forty-one percent described having had negative experiences and 8% did not remember the last time they had sober sex. Methamphetamine, mephedrone, GHB/GBL, and having had open relationships, group sex, double penetration, and fisting were significantly more prevalent. Forty-nine percent admitted being worried about chemsex use, and 18% said they needed help. A comprehensive, interdisciplinary approach is mandatory to enable the attainment of a healthy approach to one's sex life.

HIV Pre-Exposure Prophylaxis in Central and Eastern Europe-Gains and Challenges in An Ever-Changing World

Pre-exposure prophylaxis (PrEP) is an effective prevention tool for controlling the HIV epidemic. Since its approval in the United States in 2012 and Europe in 2016, it has become available on a global scale offered as a registered strategy in clinical studies or demonstration projects with a slow and steady increase. In the second quarter of 2022, PrEP became available in 78 countries globally, with around 3 million people having started using PrEP. Europe has been much slower than the rest of the world to roll out PrEP; nevertheless, currently, PrEP is nationally available and reimbursed in 21 countries; generics are available but not reimbursed in 14 countries. PrEP is not formally implemented in 20 countries, which are mostly Central and Eastern European countries. There are significant disparities between countries in terms of PrEP availability, accessibility, and usage, most likely due to social, cultural, and political differences. The major barriers to PrEP use are reported to be lack of knowledge of people in need, not being reimbursed, and low perception of HIV. PrEP uptake globally and regionally still lacks the power to have an impact on controlling the epidemic. High prioritization of PrEP targets will offer us a realistic chance of reaching the Joint United Nations Programme on HIV/AIDS (UNAIDS) goal of a 90% reduction in HIV infections by 2030 compared to 2010.

Evaluating group-sequential non-inferiority clinical trials following interim stopping: The HIV Prevention Trials Network 083 trial

BACKGROUND/AIMS

The HIV Prevention Trials Network 083 trial was a group-sequential non-inferiority trial designed to compare HIV incidence under a novel experimental regimen for HIV prevention, long-acting injectable cabotegravir, with an active-control regimen of daily oral tenofovir disoproxil fumarate/emtricitabine (brand name Truvada). In March of 2020, just as the trial had completed enrollment, the COVID-19 pandemic threatened to prevent trial participants from attending study visits and obtaining study medication, motivating the study team to update the interim monitoring plan. The Data and Safety Monitoring Board subsequently stopped the trial at the first interim review due to strong early evidence of efficacy.

METHODS

Here we describe some unique aspects of the trial's design, monitoring, analysis, and interpretation. We illustrate the importance of computing point estimates, confidence intervals, and p values based on the sampling distribution induced by sequential monitoring.

RESULTS

Accurate analysis, decision-making and interpretation of trial results rely on pre-specification of a stopping boundary, including the scale on which the stopping rule will be implemented, the specific test statistics to be calculated, and how the boundary will be adjusted if the available information fraction at interim review is different from planned. After appropriate adjustment for the sampling distribution and overrun, the HIV Prevention Trials Network 083 trial provided strong evidence that the experimental regimen was superior to the active control.

CONCLUSIONS

For the HIV Prevention Trials Network 083 trial, the difference between corrected inferential statistics and naive results was quite small-as will often be the case-nevertheless, it is appropriate to report and publish the most accurate and unbiased statistical results.

Characterizing HIV-Preventive, Plasma Tenofovir Concentrations-A Pooled Participant-level Data Analysis From Human Immunodeficiency Virus Preexposure Prophylaxis Clinical Trials

BACKGROUND

Daily dosing of tenofovir disoproxil fumarate, with or without emtricitabine, has high efficacy in preventing human immunodeficiency virus (HIV) infection when individuals are adherent. The target protective plasma concentration of tenofovir (TFV), however, is not fully understood. The aim of this study is to estimate the protective TFV plasma concentration.

METHODS

Participant data from TFV-based daily oral and topical active arms of phase 3 trials (iPrEx, VOICE, and Partners PrEP) were pooled (n = 2950). Individual specific risk scores (low and high risk) of acquiring HIV, based on an earlier placebo analysis, were created. Longitudinal TFV pharmacokinetics (PK), HIV outcome, individual risk scores and the effect of sex at birth data were integrated and analyzed using non-linear mixed effects models.

RESULTS

Around 50% of the individuals were estimated to be adherent, which differed from self-reported adherence (∼90%) and large variation between longitudinal adherence patterns were identified. Following oral administration, the estimated protective TFV trough concentration was substantially higher in high-risk females (45.8 ng/mL) compared with high-risk males (16.1 ng/mL) and to low-risk individuals (∼7.5 ng/mL). Dosing simulations indicated that high-risk women require full adherence to maintain protective levels.

CONCLUSIONS

Using the largest PK-HIV outcome database to date, we developed a population adherence-PK-risk-outcome model. Our results indicate that high-risk females need higher levels of plasma TFV to achieve HIV protection compared with males. HIV protection exceeds 90% in all populations if daily adherence is achieved.

Short-term oral pre-exposure prophylaxis against HIV-1 modulates the transcriptome of foreskin tissue in young men in Africa

Whilst short-term oral pre-exposure prophylaxis (PrEP) with antiretroviral drugs in men who have sex with men has shown protection against HIV-1 infection, the impact of this regimen on the in vivo foreskin transcriptome is unknown. We collected foreskin tissue after voluntary medical male circumcision from 144 young men (72 from Uganda and 72 from South Africa) randomized to one to two doses of either oral tenofovir (TFV) disoproxil fumarate (FTC-TDF) or tenofovir alafenamide (FTC-TAF) or no drug (untreated controls). This novel approach allowed us to examine the impact of short-term oral PrEP on transcriptome of the male genital tract. A single dose of FTC-TDF did not affect the foreskin transcriptome in relation to control arm, however one dose of FTC-TAF induced upregulation of four genes AKAP8, KIAA0141, HSCB and METTL17. Following two doses of either FTC-TDF or FTC-TAF, there was an increase in 34 differentially expressed genes for FTC-TDF and 15 for FTC-TAF, with nine DEGs in common: KIAA0141, SAFB2, CACTIN, FXR2, AKAP8, HSCB, CLNS1A, DDX27 and DCAF15. Functional analysis of differentially expressed genes revealed modulation of biological processes related to mitochondrial stress (KIAA0141, HSCB and METTL17), anti-viral and anti-inflammatory pathways (CACTIN and AKAP8). Our results show that short-course on-demand oral PrEP in men modulates genes in foreskin tissue which are likely unfavorable to HIV acquisition and replication. We also describe an upregulated expression of genes involved in diverse mitochondria biology which may potentially result in worsened mitochondria-related. These results warrant further studies to assess the role of short-course and prolonged oral PrEP on biological processes of the foreskin mucosa.

MTN-033: a Phase 1 Study Comparing Applicator versus "as Lubricant" Delivery of Rectal Dapivirine Gel

Data to inform behaviorally congruent delivery of rectal microbicides as lubricants are scant. Dapivirine (DPV) is a nonnucleoside reverse transcriptase inhibitor which has been demonstrated to be well-tolerated and efficacious in multiple clinical trials when used in a vaginal ring formulation. DPV gel administered rectally with an applicator was found to be well-tolerated in a phase 1 clinical trial. MTN-033, a single site, open label, sequence randomized, crossover study, enrolled HIV-negative men to receive 0.05% DPV gel intrarectally using an applicator (2.5 g) and self-administered on an artificial phallus as lubricant (up to 10 g). The study evaluated the pharmacokinetics (in plasma, rectal fluid, and mucosal rectal tissue), safety, acceptability, and pharmacodynamics of DPV gel when applied rectally. Statistical comparisons between methods of application were performed using mixed effects models or Wilcoxon's signed rank tests. Sixteen participants used DPV gel by applicator and 15/16 participants used gel as lubricant (mean, 1.8 g; SD, 0.8). DPV plasma AUC0-24h after use as lubricant was estimated to be 0.41 times the AUC0-24h (95% CI 0.24, 0.88) after use with applicator. While DPV was quantifiable in plasma and luminal fluid, it was not quantifiable in tissue for both applicator and as lubricant administration. No related adverse events (AE) were reported, and 15/15 participants felt the gel was easy to use. Evidence of local delivery and systemic absorption of DPV when dosed as an anal lubricant supports the feasibility and potential for development of lubricant-delivered rectal microbicides. There were no safety concerns associated with use of DPV gel and participants reported finding it easy to use. However, lower DPV exposure in plasma and lack of quantifiable DPV in rectal tissue indicate that higher potency, concentration, and longer half-life antiretrovirals with optimized formulations will be needed to achieve protective tissue concentrations.

[HIV preexposure prophylaxis with tenofovir disoproxil fumarate/emtricitabine: What about safety?]

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is a combination of antiretroviral regimen, tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) that has been shown to prevent HIV transmission. It had been regulated through a temporary recommendation use since December 2015 and had marketing authorization in France since March 2017. As, this product is proposed for adults and adolescents safe from HIV but at high risk of infection, the question is to know if there is a safety concern about this use.

METHODS

A request has been made in the French national pharmacovigilance database (ANPV) and VIGILYZE for an extraction of all cases containing TDF/FTC as suspect drugs in PrEP use. In the second part, we did a literature review in PubMED with MeSH terms and an analysis of the results of the American, English and French initial clinical trials was performed.

RESULTS

In both database, 808 cases correspond to an indication of HIV prexposure prophylaxis who represent 2058 adverse effects (AEs) mainly distributed in gastro-intestinal disorders (38.5%), general disorders (16.8%) and 62 cases of seroconversion. We identify 24% of unexpected AEs including 12% of serious AEs in the French database. In literature review, there are no unexpected AEs published, the AEs are mainly gastro-intestinal disorders. There was no significant difference in the AE profile compared to the HIV-infected population treated with TDF/FTC.

CONCLUSION

Data from the ANPV, combined with data from the worldwide pharmacovigilance database, show that the most commonly observed AEs are gastrointestinal, mainly nausea, vomiting and diarrhea. A significant number of asthenia and fatigue are also observed. These AEs are well described in the SMPc. However, we have little data, which can be explained by a probable under-reporting of AEs. We identify 24% of unexpected and potentially serious adverse effects in France mainly among chemsex users. Based on these results, our study confirms the safety of PrEP.

Retrospective audit of a convenience cohort of individuals on HIV pre-exposure prophylaxis in Alberta, Canada

BACKGROUND

We undertook an audit of a province-wide HIV pre-exposure prophylaxis (PrEP) program in Alberta (Canada).

METHODS

A retrospective record review of individuals accessing PrEP in Alberta included demographics, PrEP indication(s), and reported non-prescription drug and alcohol use from March 2016 to June 2019. Hepatitis A, B, C, HIV and syphilis serology, serum creatinine, and nucleic acid amplification tests testing for chlamydia and gonorrhea were collected. Descriptive statistics, incidence, and prevalence were calculated.

RESULTS

A total of 511 participants were seen at STI, sexual, and reproductive health clinics and private family practitioner (FP) offices; 98.4% (503) were men, median age was 34 years (IQR 28-43 years), and 89.8% (459) were gay or bisexual men who have sex with men. Non-prescription drug use was reported by 39.3% (201) and alcohol use by 55.4% (283). 94.3% (482) reported condomless anal sex in the past 6 months. Testing rates were high (>95%) for all tests except for chlamydia and gonorrhea at the first follow-up visit 89.6%; (3-4 months). There was one HIV seroconversion. The incidence of new bacterial STIs was high: chlamydia 17 cases per 100 person-years (95% CI 13.5% to 21.4%), gonorrhea 11.14 cases per 100 person-years (95% CI 8.3% to 15.0%), and syphilis 1.94 cases per 100 person-years (95% CI 0.73% to 5.12%).

CONCLUSIONS

Following implementation of a provincial program for PrEP in Alberta, PrEP initiation and continuation was feasible in a range of settings and by both specialists and FPs.

Loss to Follow-Up from HIV Pre-Exposure Prophylaxis Care in Men Who Have Sex with Men in West Africa

Loss to follow-up (LTFU) from HIV pre-exposure prophylaxis (PrEP) care compromises the goal of HIV elimination. We investigated the proportion of LTFU and associated risk factors among men who have sex with men (MSM) enrolled in a PrEP demonstration project in Burkina Faso, Côte d'Ivoire, Mali, and Togo. CohMSM-PrEP, a prospective cohort study, was conducted between November 2017 and June 2021 in community-based clinics. MSM aged 18 years or older at substantial risk of HIV infection received a comprehensive prevention package, including PrEP and peer education. LTFU was defined as not returning to the clinic for six months. Associated risk factors were investigated using a time-varying Cox's model. Of 647 participants followed up for a median time of 15 months, 372 were LTFU (57.5%). LTFU was associated with younger age (adjusted hazard ratio [95% Confidence Interval]; 1.50 [1.17-1.94]), unemployment (1.33 [1.03-1.71]), depression (1.63 [1.12-2.38]), and perceiving no HIV risk with stable male partners (1.61 [1.23-2.10]). Contacting peer educators outside of scheduled visits was protective (0.74 [0.56-0.97]). Our findings show that LTFU from PrEP care in West African MSM is a major challenge to achieving HIV elimination, but that the involvement of peer educators in PrEP delivery helps to limit LTFU by providing users with adequate support.

Real-life cohort experience after implementing HIV pre-exposure prophylaxis for one year in northwest Spain

Introduction

Pre-exposure prophylaxis (PrEP) has become a useful tool to reduce the transmission of human immunodeficiency virus (HIV) in key populations. In this article we assessed the effectiveness, safety, adherence, sexually transmitted infections (STIs) dynamics, and frequency of anal dysplasia among a real-life cohort of PrEP users in Northwest Spain.

Methods

A retrospective cohort study was undertaken in the Alvaro-Cunqueiro Hospital, Vigo which included every individual who started daily emtricitabine/tenofovir-disoproxil-fumarate (FTC/TDF) between November-2019 and October-2021. Clinical and epidemiological data were obtained from the patient's medical records. The effectiveness and safety of FTC/TDF were assessed by HIV serology and renal function monitoring every 3 months. Anal, urethral, and oropharyngeal exudates were collected quarterly after the baseline visit.

Results

A total of 126 individuals were considered eligible, most of the participants had previously been diagnosed with a STI (60.3%), 22% had consumed recreational drugs in the year prior, and 13% had engaged in chemsex. At the end of the follow-up, no cases of HIV infection were detected; 3 patients had discontinued FTC/TDF because of side effects but none of them had presented renal toxicity. In addition, the diagnosis of STIs during the follow-up was common (100 cases in 54 patients). Moreover, engagement in chemsex was more common within this latter group (22 vs. 6%, p = 0.013). Among the study population included in the anal screening programme, the frequency of dysplasia was 9%.

Conclusions

FTC/TDF was effective, safe, and tolerable in a real-life cohort; adherence remained high throughout the study period (79%). However, a high number of STIs were diagnosed, especially among patients who engaged in chemsex.

Effectiveness of interventions aimed at reducing HIV acquisition and transmission among gay and bisexual men who have sex with men (GBMSM) in high income settings: A systematic review

INTRODUCTION

HIV transmission continues among gay and bisexual men who have sex with men (GBMSM), with those who are younger, or recent migrants, or of minority ethnicity or who are gender diverse remaining at increased risk. We aimed to identify and describe recent studies evaluating the effectiveness of HIV prevention interventions for GBMSM in high income countries.

METHODS

We searched ten electronic databases for randomized controlled trials (RCTs), conducted in high income settings, and published since 2013 to update a previous systematic review (Stromdahl et al, 2015). We predefined four outcome measures of interest: 1) HIV incidence 2) STI incidence 3) condomless anal intercourse (CLAI) (or measure of CLAI) and 4) number of sexual partners. We used the National Institute for Health and Care Excellence (UK) Quality Appraisal of Intervention Studies tool to assess the quality of papers included in the review. As the trials contained a range of effect measures (e.g. odds ratio, risk difference) comparing the arms in the RCTs, we converted them into standardized effect sizes (SES) with 95% confidence intervals (CI).

RESULTS

We identified 39 original papers reporting 37 studies. Five intervention types were identified: one-to-one counselling (15 papers), group interventions (7 papers), online interventions (9 papers), Contingency Management for substance use (2 papers) and Pre-exposure Prophylaxis (PrEP) (6 papers). The quality of the studies was mixed with over a third of studies rated as high quality and 11% rated as poor quality. There was some evidence that one-to-one counselling, group interventions (4-10 participants per group) and online (individual) interventions could be effective for reducing HIV transmission risk behaviours such as condomless anal intercourse. PrEP was the only intervention that was consistently effective at reducing HIV incidence.

CONCLUSIONS

Our systematic review of the recent evidence that we were able to analyse indicates that PrEP is the most effective intervention for reducing HIV acquisition among GBMSM. Targeted and culturally tailored behavioural interventions for sub-populations of GBMSM vulnerable to HIV infection and other STIs should also be considered, particularly for GBMSM who cannot access or decline to use PrEP.

A retrospective analysis of bone loss in tenofovir-emtricitabine therapy for HIV PrEP

BACKGROUND

Tenofovir-Emtricitabine (TDF-FTC) is known to cause bone loss in about 1-3% of HIV treated patients. Current studies lack evidence in minority groups and long-term bone loss effects in PrEP patients.

SETTING

To address the risk of osteopenia/osteoporosis in patients on TDF-FTC therapy for HIV PrEP and to address the breakthrough incidence of HIV.

METHODS

A retrospective analysis was performed in Kaiser Permanente patients from 2012-2021. Patients on TDF-FTC for PrEP without any prior history of osteopenia/osteoporosis (N = 7698) were analyzed to determine the relationship between PrEP adherence and osteopenia/osteoporosis. Descriptive statistics and Cox proportional hazards model were used to compare and analyze patient characteristics between those who developed osteopenia/osteoporosis and those who didn't.

RESULTS

3% were found to have osteopenia/osteoporosis. Patients who developed osteopenia/osteoporosis were more likely to have a proportion of days covered (PDC) ratio ≥90%, older, had history of Hep B, DM, CVD, CKD, hypertension, and baseline eGFR ≥90 mL/min/1.73 m². Kaplan-Meier curve showed the event-free rate of osteopenia/osteoporosis decreased with time, with a greater reduction in patients with high adherence. Survival analysis showed only PDC of ≥90% was significantly associated with the risk of osteopenia/osteoporosis when adjusted. No incidence of HIV infection was detected.

CONCLUSIONS

This retrospective cohort analysis showed that TDF-FTC offered superior PrEP protection. Although high PrEP adherence ensured protection from HIV infection, it was significantly associated with a higher risk of developing osteopenia/osteoporosis. These findings suggest that routine check-ups for osteopenia/osteoporosis may be needed.

Perceived influence of alcohol consumption, substance use, and mental health on PrEP adherence and condom use among PrEP-prescribed gay, bisexual, and other men-who-have-sex-with-men: a qualitative investigation

BACKGROUND

Gay, bisexual, and other men-who-have-sex-with-men (GBMSM) continue to be disproportionately affected by Human Immunodeficiency Virus (HIV). Although HIV pre-exposure prophylaxis (PrEP) offers an effective means of reducing incident HIV among this population, the HIV-preventive success of oral-based PrEP is contingent upon regimen adherence. Elevated rates of alcohol-, substance use-, and mental health-related issues among GBMSM potentially hinder PrEP-taking efforts, however the evidence for this remains mixed. Accordingly, the present study entailed a comprehensive qualitative investigation to explore PrEP-prescribed GBMSM's perceptions surrounding the influence of alcohol, substance use, and mental health on PrEP adherence.

METHODS

PrEP-prescribed GBMSM (age ≥ 18 years; prescribed PrEP for ≥ 3 months) were recruited from two PrEP-delivery clinics in Toronto, Canada for focus groups as part of the formative phase of an alcohol-, substance use-, and mental health-focused randomized controlled intervention trial. Focus group discussions qualitatively explored perceived strengths and barriers associated with adherence to PrEP treatment; with an emphasis on alcohol, substance use, and mental health concerns. Condom use among PrEP-prescribed GBMSM within the context of these concerns was also discussed.

RESULTS

A total of five focus groups involving 35 GBMSM were conducted (4-10/group; mean age = 42.4; white = 71.4%). Although participants themselves generally reported successfully adhering to their PrEP regimens-resulting from a strong, underlying motivation for self-care-they recognized the detrimental impact that alcohol, substance use, and mental health had on adherence among their peers. In this regard, alcohol and substances were perceived as detracting from adherence only when consumption was excessive or temporally linked to PrEP dosing. Pronounced mental health issues (e.g., severe depression) were also seen as hindering adherence, although these effects were nuanced and perceived as person-dependent. Alcohol and substances were linked to condomless sex, regardless of PrEP use, and PrEP was therefore viewed as an HIV-protective 'safety net.'

CONCLUSIONS

Overall, findings suggest that PrEP adherence can often be successfully achieved in the presence of alcohol-, substance use-, and mental health-related issues. Augmenting self-care, and addressing pronounced addictions- and mental health-related concerns, may enhance PrEP treatment among GBMSM.

A Qualitative Exploration of Various Stigmas Impacting HIV Pre-Exposure Prophylaxis (PrEP) Uptake Among African American Young Adults

Pre-exposure prophylaxis (PrEP) has promise for reducing racial/ethnic HIV disparities; yet, acceptance among African Americans remains low. PrEP-related stigmas may impact uptake, but this is understudied. This study examines mechanisms by which stigma impacts PrEP acceptance among various priority African American populations. Focus group data from 63 African American young adults (aged 18-29 years) in Louisville, Kentucky, explore how various stigmas impact attitudes toward PrEP. Data were analyzed using grounded theory analytic techniques. PrEP stigma, HIV stigma, sexual behavior stigma, and homophobia/transphobia individually reduce PrEP uptake. These stigmas also interact synergistically to undermine PrEP acceptance. Key challenges resulting from various stigmas and their interactions include medical hesitancy, lack of perceived susceptibility based on gender and sexuality, the role of gender norms in HIV prevention, and deprioritizing HIV prevention due to social rejection. Interventions to increase awareness, destigmatize PrEP, remediate social marginalization related to identity, HIV status, and gendered perceptions of sexual risk, as well as more focus on diverse priority groups, are needed to present PrEP as a viable HIV prevention option for African American communities. More research is needed to optimize strategies that address stigma and increase acceptance of novel HIV prevention technologies.

HIV Pre-Exposure Prophylaxis (PrEP) among men who have sex with men: peer communication, engagement and social networks

Abstract HIV Pre-Exposure Prophylaxis (PrEP) has renewed optimism in controlling the HIV epidemic, despite its continued growth among men who have sex with men (MSM). The popularity of dating-sexual dating apps and digital media platforms in exchanging information and experiences about PrEP on peer social networks is recognized. However, studies on contexts, motivations, and scope in HIV prevention are scarce. The article aims to understand the dynamics of virtual and face-to-face peer networks among MSM for the decision to use PrEP, its disclosure, and publicity. Qualitative study using semi-structured interviews with 48 PrEP users from five Brazilian cities. Most interviewees share information and experiences about PrEP in peer social networks. However, its publication reveals tensions arising from the permanence of stigmas associated with homosexuality and HIV. The protagonism in exposing the use of PrEP expresses commitment to attracting new users. The relevance of peer social networks in sharing experiences and information about PrEP has the potential to diversify the target audience and expand and democratize PrEP coverage in the country.

HIV Pre-Exposure Prophylaxis (PrEP) among men who have sex with men: peer communication, engagement and social networks

HIV Pre-Exposure Prophylaxis (PrEP) has renewed optimism in controlling the HIV epidemic, despite its continued growth among men who have sex with men (MSM). The popularity of dating-sexual dating apps and digital media platforms in exchanging information and experiences about PrEP on peer social networks is recognized. However, studies on contexts, motivations, and scope in HIV prevention are scarce. The article aims to understand the dynamics of virtual and face-to-face peer networks among MSM for the decision to use PrEP, its disclosure, and publicity. Qualitative study using semi-structured interviews with 48 PrEP users from five Brazilian cities. Most interviewees share information and experiences about PrEP in peer social networks. However, its publication reveals tensions arising from the permanence of stigmas associated with homosexuality and HIV. The protagonism in exposing the use of PrEP expresses commitment to attracting new users. The relevance of peer social networks in sharing experiences and information about PrEP has the potential to diversify the target audience and expand and democratize PrEP coverage in the country.

Next Generation Pre-Exposure Prophylaxis for Young Men who have Sex with Men: Lessons from System and Provider-level barriers to oral PrEP

Next generation pre-exposure prophylaxis (PrEP) modalities that do not require daily regimens may address some of the barriers to daily oral PrEP among young men who have sex with men (YMSM). We conducted online semi-structured interviews with 30 YMSM to examine experiences and preferences related to HIV prevention care that may inform implementation of next generation PrEP. Barriers to PrEP care included initiating conversations about sexuality with providers; confidentiality concerns regarding disclosure of sexual practices and PrEP use to family; gaps in access to healthcare; and limited availability of affordable health services. Future implementation of next generation PrEP may benefit from providers addressing confidentiality concerns when discussing PrEP with YMSM; PrEP programs accounting for discontinuities in healthcare access among YMSM while strengthening access to affordable services; and collaborations between generalist providers and specialized clinics and providers to address providers' education needs, which may increase as next generation PrEP becomes available. We have linked affiliation 9 to author name "Katie B. Biello". Please check and confirm. Okay!

PrEP uptake and delivery setting preferences among clients visiting six healthcare facilities in Eswatini

Due to the high HIV incidence among the general population of Eswatini, pre-exposure prophylaxis (PrEP) for HIV-exposed individuals is recommended. However, little is known about PrEP uptake and preferences in PrEP delivery healthcare setting among the general population. We conducted a secondary analysis of a randomized trial that aimed to increase PrEP uptake. All clients eligible for PrEP in one of six public-sector healthcare facilities in Eswatini were included. PrEP uptake was stratified by initial reason for visit (e.g. outpatient). Preferences in PrEP delivery setting were collected among those clients who initiated PrEP. A total of 1782 clients had their HIV acquisition risk assessed. Of these, 72% (1277/1782) were considered at risk by healthcare providers and, among them, 40% (517/1277) initiated PrEP. Uptake was higher among clients visiting specifically to initiate PrEP (93%), followed by HIV testing visits (45.8%) and outpatient visits (40%). Among those who initiated PrEP, preferred delivery settings were outpatient services (31%), HIV testing services (26%), family planning (21%) and antenatal services (14%). Men or those at high risk of HIV acquisition were more likely to prefer HIV testing and outpatient services, while young women were more likely to visit and express a preference for antenatal and family planning services. Outpatient services and HIV testing services could be preferable choices for PrEP delivery integration, due to the high PrEP uptake and delivery setting preferences of the populations who use these services. Antenatal and family planning could also be considered with a view to targeting the youngest women.

Pre-exposure Prophylaxis Discontinuation During the COVID-19 Pandemic Among Men Who Have Sex With Men in a Multisite Clinical Cohort in the United States

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic continues to put strain on health systems in the United States, leading to significant shifts in the delivery of routine clinical services, including those offering HIV pre-exposure prophylaxis (PrEP). We aimed to assess whether individuals discontinued PrEP use at higher rates during the COVID-19 pandemic and the extent to which disruptions to usual clinical care were mitigated through telehealth.

METHODS

Using data from an ongoing prospective cohort of men who have sex with men (MSM) newly initiating PrEP in 3 mid-sized cities (n = 195), we calculated the rate of first-time discontinuation of PrEP use in the period before the COVID-19 pandemic and during the COVID-19 pandemic and compared these rates using incidence rate ratios (IRRs). Furthermore, we compared the characteristics of patients who discontinued PrEP use during these periods with those who continued to use PrEP during both periods.

RESULTS

Rates of PrEP discontinuation before the COVID pandemic and during the COVID-19 pandemic were comparable [4.29 vs. 5.20 discontinuations per 100 person-months; IRR: 1.95; 95% confidence interval (CI): 0.83 to 1.77]. Although no significant differences in the PrEP discontinuation rate were observed in the overall population, the rate of PrEP discontinuation increased by almost 3-fold among participants aged 18-24 year old (IRR: 2.78; 95% CI: 1.48 to 5.23) and by 29% among participants covered by public insurance plans at enrollment (IRR: 1.29; 95% CI: 1.03 to 5.09). Those who continued to use PrEP were more likely to have had a follow-up clinical visit by telehealth in the early months of the pandemic (45% vs. 17%).

CONCLUSIONS

In this study, rates of PrEP discontinuation were largely unchanged with the onset of the COVID-19 pandemic. The use of telehealth likely helped retain patients in PrEP care and should continue to be offered in the future.

Who is using PrEP on-demand? Factors associated with PrEP use modality among Black and Hispanic/Latino emerging adults

Pre-exposure prophylaxis (PrEP) is a highly efficacious HIV prevention medication, yet Black and Hispanic/Latino sexual minority men's and gender diverse individuals' (SMMGD) PrEP use is limited due to factors such as PrEP barriers and anticipated PrEP stigma. Although most individuals who use PrEP take it as a daily regimen, there is evidence that many SMMGD are interested in using "on-demand" (also known as event-driven or intermittent or 2-1-1) PrEP. We used stepwise multinomial logistic regression to explore factors associated with on-demand, daily, and no PrEP use among 820 Black and Hispanic/Latino SMMGD ages 18-29 in the United States. We found that greater reported PrEP barriers were associated with higher odds of using PrEP on-demand or not using PrEP compared to daily PrEP use. More past 3-month sex partners and greater comfort telling others about PrEP use were associated with lower odds of on-demand compared to daily PrEP use. In addition, compared to daily PrEP use, more past 3-month sex partners, greater comfort telling others about PrEP use, and higher anticipated PrEP stigma were associated with lower odds of no current PrEP use compared to daily PrEP use. Findings may inform clinical practices and interventions to promote PrEP uptake and adherence.

Episodic Use of Pre-Exposure Prophylaxis Among Young Cisgender Women in Siaya County, Kenya

The concept "seasons of risk" promotes use of pre-exposure prophylaxis (PrEP) only during periods of HIV risk. PrEP guidelines are aligned on daily use in women having vaginal sex during a risk period, and daily use for 28 days after the last potential exposure is recommended. However, when starting a "season of risk," guidelines vary on "time to protection," and unknowns remain in pharmacological research on PrEP protection in this population. During our iterative research on PrEP persistence using photovoice and in-depth interviews, we identified an ineffective pattern of PrEP use based on current guidelines-that is, routine, episodic use-among young cisgender women (YCW) in Siaya County, Kenya. Through same-group (n = 33 participants) and mixed-group (n = 31 participants) photovoice activities with YCW taking PrEP and female peers, participants explained that YCW associate their HIV risk with the sexual behaviors of their male partners who frequently travel from home. PrEP is considered unnecessary when partners are away because of no perceived risk. YCW re-start PrEP on or around the day of their partners' return because of heightened risk perceptions. Among the YCW interviewed (n = 18), nearly all of their partners traveled for about 1 week to 1 month at a time; about one-third of these women reported stopping PrEP during their partners' absence and re-starting it soon before or immediately upon their partners' arrival home. Additional research is critically needed to better inform PrEP guidelines and the decisions adolescent girls and young women make on how to use PrEP based on their risk context. In the interim, counseling on current dosing guidance when stopping and re-starting PrEP within a "season of risk" is needed.

The Ethical Relevance of "Alternatives" in Health Care Priority Setting - The Case of Preexposure Prophylaxis (PrEP) of HIV

Preexposure prophylaxis for HIV is a drug that reduces the risk for an HIV-negative person to acquire HIV if taken prior to sex. It has been suggested that it is important for resource allocation decisions that there are alternatives (such as abstinence, masturbation, etc.) for individuals potentially benefitted by this prophylaxis. In this paper we explore this idea from an ethical perspective in relation to three notions often discussed in priority setting ethics, namely responsibility, outcomes, and severity of disease. While the relevance of alternatives may be explained in terms by responsibility-sensitive priority setting, such a view comes with several challenges. We then discuss two other ways in which this intuition could be better explained: (a) in terms of total outcome of health, and (b) in terms of severity of the condition.

Pharmacogenomics of drug transporters for antiretroviral long-acting pre-exposure prophylaxis for HIV

The use of antiretrovirals (ARVs) as oral, topical, or long-acting pre-exposure prophylaxis (PrEP) has emerged as a promising strategy for HIV prevention. Clinical trials testing Truvada® [tenofovir disoproxil fumarate (TDF)/tenofovir (TFV) and emtricitabine (FTC)] as oral or topical PrEP in African women showed mixed results in preventing HIV infections. Since oral and topical PrEP effectiveness is dependent on adequate drug delivery and availability to sites of HIV infection such as the blood and female genital tract (FGT); host biological factors such as drug transporters have been implicated as key regulators of PrEP. Drug transporter expression levels and function have been identified as critical determinants of PrEP efficacy by regulating PrEP pharmacokinetics across various cells and tissues of the blood, renal tissues, FGT mucosal tissues and other immune cells targeted by HIV. In addition, biological factors such as genetic polymorphisms and genital inflammation also influence drug transporter expression levels and functionality. In this review, drug transporters and biological factors modulating drug transporter disposition are used to explain discrepancies observed in PrEP clinical trials. This review also provides insight at a pharmacological level of how these factors further increase the susceptibility of the FGT to HIV infections, subsequently contributing to ineffective PrEP interventions in African women.

Socio-behavioral correlates of pre-exposure prophylaxis use and correct adherence in men who have sex with men in West Africa

BACKGROUND

Multiple barriers compromise pre-exposure prophylaxis (PrEP) engagement (i.e., use and adherence) in men who have sex with men (MSM). In low/middle-income countries, little is known about PrEP engagement in this population. In West Africa, the CohMSM-PrEP study was one of the rare interventions providing PrEP to MSM. We estimated PrEP use and correct adherence rates in CohMSM-PrEP, together with associated factors over time.  METHODS: CohMSM-PrEP recruited MSM in four community-based clinics in Mali, Côte d'Ivoire, Burkina Faso, and Togo. Quarterly follow-up included collecting socio-behavioral data, and providing a comprehensive HIV prevention package, PrEP (daily or event-driven), and peer educator (PE)-led counselling. Using repeated measures, multivariate generalized estimating equations models were used to identify factors associated with self-reported i) PrEP use and ii) correct PrEP adherence during participants' most recent anal intercourse (defined as four pills/week for daily users and 2 + 1 + 1 for event-driven users).

RESULTS

Five hundred twenty participants were included with a median follow-up time of 12 months (IQR 6-21). Of the 2839 intercourses declared over the follow-up period, PrEP use was self-reported for 1996 (70%), and correct PrEP adherence for 1461 (73%) of the latter. PrEP use was higher in participants who also attended participating clinics outside of scheduled visits (adjusted odds ratio (aOR) [95% Confidence Interval, CI], p-value; 1.32[1.01-1.71], 0.040), and in those who practiced condomless anal sex (1.86[1.54-2.24], < 0.001). Correct adherence was higher in those who often contacted PE outside of scheduled visits (2.16[1.01-4.64], 0.047) and in participants who adopted receptive/versatile sexual positions with stable partners (1.36[1.03-1.81], 0.030). Instead, after an interaction effect between financial situation and regimen was tested, it was lower in event-driven users with a difficult/very difficult financial situation (comfortable/just making ends meet & daily, 4.19[2.56-6.86], < 0.001; difficult/very difficult & daily, 6.47[4.05-10.30], < 0.001; comfortable/just making ends meet & event-driven, 1.63[1.22-2.17], 0.001), and in participants who felt alone (0.76[0.58-0.99], 0.042).

CONCLUSIONS

Community-based clinic attendance and PE contact outside of scheduled visits were both associated with higher PrEP engagement, but some socially and economically marginalized participants struggled with adherence. As scale-up continues in West Africa, we recommend implementing community-based interventions and providing extra support for vulnerable users to ensure adequate PrEP engagement.

Low incidence of HIV infection and decreasing incidence of sexually transmitted infections among PrEP users in 2020 in Germany

Introduction

Objectives of this study, as part of a nation-wide HIV pre-exposure prophylaxis (PrEP) evaluation project, were to determine the incidence of infections with HIV, chlamydia, gonorrhea, syphilis, hepatitis A/B/C in persons using PrEP, and to describe the health care funded PrEP use in Germany. Additionally, factors associated with chlamydia/gonorrhea and syphilis infections were assessed.

Methods

Anonymous data of PrEP users were collected at 47 HIV-specialty centers from 09/2019–12/2020. Incidence rates were calculated per 100 person years (py). Using longitudinal mixed models, we analyzed risk factors associated with sexually transmitted infections (STIs).

Results

4620 PrEP users were included: 99.2% male, median age 38 years (IQR 32–45), 98.6% men who have sex with men (MSM). The median duration of PrEP exposure was 451 days (IQR 357–488), totaling 5132 py. Four HIV infections were diagnosed, incidence rate 0,078/100py (95% CI 0.029–0.208). For two, suboptimal adherence was reported and in the third case, suboptimal adherence and resistance to emtricitabine were observed. One infection was likely acquired before PrEP start. Incidence rates were 21.6/100py for chlamydia, 23.7/100py for gonorrhea, 10.1/100py for syphilis and 55.4/100py for any STI and decreased significantly during the observation period. 65.5% of syphilis, 55.6% of chlamydia and 50.1% of gonorrhea cases were detected by screening of asymptomatic individuals. In a multivariable analysis among MSM younger age, PrEP start before health insurance coverage and daily PrEP were associated with greater risk for chlamydia/gonorrhea. Symptom triggered testing and a history of STI were associated with a higher risk for chlamydia/gonorrhea and syphilis. A significantly lower risk for chlamydia/gonorrhea and syphilis was found for observations during the COVID-19 pandemic period.

Conclusions

We found that HIV-PrEP is almost exclusively used by MSM in Germany. A very low incidence of HIV infection and decreasing incidence rates of STIs were found in this cohort of PrEP users. The results were influenced by the SARS-CoV-2 pandemic. Rollout of PrEP covered by health insurance should be continued to prevent HIV infections. Increased PrEP availability to people at risk of HIV infection through the elimination of barriers requires further attention. Investigation and monitoring with a longer follow-up would be of value.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-022-01919-3.

HIV prevention for the next decade: Appropriate, person-centred, prioritised, effective, combination prevention

UNAIDS and a broad range of partners have collaborated to establish a new set of HIV prevention targets to be achieved by 2025 as an intermediate step towards the sustainable development target for 2030.The number of new HIV infections in the world continues to decline, in part due to the extraordinary expansion of effective HIV treatment. However, the decline is geographically heterogeneous, with some regions reporting a rise in incidence. The incidence target that was agreed for 2020 has been missed.A range of exciting new HIV prevention technologies have become available or are in the pipeline but will only have an impact if they are accessible and affordable and delivered within systems that take full account of the social and political context in which most infections occur. Most new infections occur in populations that are marginalised or discriminated against due to structural, legal, and cultural barriers.The new targets imply a new approach to HIV prevention that emphasises appropriate, person-centred, prioritised, effective, combination HIV prevention within a framework that reduces existing barriers to services and acknowledges heterogeneity, autonomy, and choice.These targets have consequences for people working in HIV programmes both for delivery and for monitoring and evaluation, for health planners setting local and national priorities, and for funders both domestic and global. Most importantly, they have consequences for people who are at risk of HIV exposure and infection.Achieving these targets will have a huge impact on the future of the HIV epidemic and put us back on track towards ending AIDS as a public health threat by 2030.

Pleasure and PrEP: A Systematic Review of Studies Examining Pleasure, Sexual Satisfaction, and PrEP

Pre-exposure prophylaxis (PrEP) is an effective form of Human Immunodeficiency Virus (HIV) prevention for people at potential risk for exposure. Despite its demonstrated efficacy, PrEP uptake and adherence have been discouraging, especially among groups most vulnerable to HIV transmission. A primary message to persons who are at elevated risk for HIV has been to focus on risk reduction, sexual risk behaviors, and continued condom use, rarely capitalizing on the positive impact on sexuality, intimacy, and relationships that PrEP affords. This systematic review synthesizes the findings and themes from 16 quantitative, qualitative, and mixed methods studies examining PrEP motivations and outcomes focused on sexual satisfaction, sexual pleasure, sexual quality, and sexual intimacy. Significant themes emerged around PrEP as increasing emotional intimacy, closeness, and connectedness; PrEP as increasing sexual options and opportunities; PrEP as removing barriers to physical closeness and physical pleasure; and PrEP as reducing sexual anxiety and fears. It is argued that positive sexual pleasure motivations should be integrated into messaging to encourage PrEP uptake and adherence, as well as to destigmatize sexual pleasure and sexual activities of MSM.

Clinical Considerations in the Selection of Preexposure Prophylaxis for HIV Prevention in Canada

According to the Public Health Agency of Canada, approximately 62,050 people were living with HIV in Canada in 2018, and of those, 13% were undiagnosed. Currently, no single strategy provides complete protection or is universally effective across all demographic groups at risk for HIV. However, HIV preexposure prophylaxis (PrEP) is the newest HIV prevention strategy that shows promise. To date, two products have received an indication for PrEP by Health Canada: emtricitabine/tenofovir disoproxil fumarate (Truvada®; FTC/TDF) and emtricitabine/tenofovir alafenamide (Descovy®; FTC/TAF). Despite the high efficacy of these PrEP intervention methods, access to PrEP in Canada remains low. Identifying and addressing barriers to PrEP access, especially in high-risk groups, are necessary to reduce HIV transmission in Canada. While guidelines published by the Center for Disease Control and Prevention (CDC) include FTC/TAF information, the efficacy of FTC/TAF for PrEP has not yet been considered in Canada's clinical practice guidelines. Thus, the current paper reviews data regarding the use of FTC/TDF and FTC/TAF for PrEP, which may be useful for Canadian healthcare providers when counseling and implementing HIV prevention methods. The authors highlight these data in relation to various at-risk populations and review ongoing clinical trials investigating novel PrEP agents. Overall, FTC/TDF PrEP is effective for many populations, including men who have sex with men, transgender women, heterosexuals with partners living with HIV, and people who use drugs. While there is fewer data reported on the efficacy of FTC/TAF to date, recent clinical trials have demonstrated noninferiority of FTC/TAF in comparison to FTC/TDF. Notably, as studies have shown that FTC/TAF maintains renal function and bone mineral density to a greater extent than FTC/TDF, FTC/TAF may be a safer option for patients experiencing renal and/or bone dysfunction, for those at risk of renal and bone complications, and for those who develop FTC/TDF-related adverse events.

Modeling the Probability of HIV Infection over Time in High-Risk Seronegative Participants Receiving Placebo in Five Randomized Double-Blind Placebo-Controlled HIV Pre-Exposure Prophylaxis Trials: A Patient-Level Pooled Analysis

The World Health Organization recommends pre-exposure prophylaxis (PrEP) for individuals at substantial risk of HIV infection. The aim of this analysis is to quantify the individual risk of HIV infection over time, using a large database of high-risk individuals (n = 5583). We used data from placebo recipients in five phase III PrEP trials: iPrEx, conducted in men who have sex with men and transgender women; VOICE, conducted in young women at high sexual risk; Partners PrEP, conducted in HIV serodiscordant heterosexual couples; TDF2, conducted in high-risk heterosexual men and women; and BTS, conducted in persons who inject drugs. The probability of HIV infection over time was estimated using NONMEM7.4. We identified predictors of HIV risk and found a substantial difference in the risk of infection among and within trial populations, with each study including a mix of low, moderate, and high-risk individuals (p < 0.05). Persons who were female at birth were at a higher risk of HIV infection than people who were male at birth. Final models were integrated in a tool that can assess person-specific risk and simulate cumulative HIV risk over time. These models can be used to optimize future PrEP clinical trials by identifying potential participants at highest risk.

The effect of PrEP uptake and adherence on the spread of HIV in the presence of casual and long-term partnerships

A model with both casual and long-term partnerships is considered with respect to the impact of a pre-exposure prophylaxis (PrEP) on the spread of HIV. We consider the effect of the effectiveness of PrEP, the rate that susceptible individuals choose to take PrEP, and compliance with the daily dose of the pre-exposure prophylaxis. The rate of infection in long-term partnerships is computed using a linearized expected value as a means for including the nonlocal effects of long-term partnerships while maintaining computational feasibility. The reproduction numbers for models with casual partnerships, long-term partnerships, and a combination of both are analytically computed and global stability of both disease-free and endemic equilibria is shown. Sensitivity and PRCC analysis results suggest that increasing the compliance among the current PrEP users is a more effective strategy in the fight against the HIV epidemic than increased coverage with poor compliance. Furthermore, an analysis of the reproduction number shows that models with either casual or monogamous long-term partnerships can reach the desired $ R_0 < 1 $ threshold for high enough levels of compliance and uptake, however, a model with both casual and monogamous long-term partnerships will require additional interventions. Methods highlighted in this manuscript are applicable to other incurable diseases or diseases with imperfect vaccines effected by long-term partnerships.

Impact of daily, oral pre-exposure prophylaxis on the risk of bacterial sexually transmitted infections among cisgender women: a systematic review and narrative synthesis

Background: There are concerns that the use of pre-exposure prophylaxis (PrEP) may result in an increased incidence of sexually transmitted infections (STIs). Evidence for this is mixed and has mostly been based on reviews focussed on gay and bisexual men and transgender women, while none have summarised evidence in cisgender women. Methods: We conducted a systematic review to explore whether daily, oral PrEP use is associated with changes in bacterial STI occurrence (diagnoses or self-reported) and/or risk among HIV seronegative cisgender women (ciswomen). The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool. Results: We included 11 full text articles in a narrative synthesis, with the studies published between 2012 and 2021. The studies were mostly based in Africa (n=7, 63.6%) and reported on 3168 ciswomen using PrEP aged 16-56 years. Studies had marked differences in variables, including measurements and definitions (e.g., STI type) and limited data available looking specifically at ciswomen, principally in studies with both male and female participants. The limited evidence suggests that PrEP use is not associated with increased STI rates in ciswomen generally; however, adolescent girls and young women in Sub Saharan Africa have a higher prevalence of bacterial STIs prior to PrEP initiation, compared to adult ciswomen and female sex workers. Conclusions: We suggest future PrEP research make efforts to include ciswomen as study participants and report stratified results by gender identity to provide adequate data to inform guidelines for PrEP implementation. PROSPERO registration: CRD42019130438.

A Demedicalized Model to Provide PrEP in a Sexual Health Clinic

BACKGROUND

Sexual health clinics (SHCs) serve large numbers of patients who might benefit from preexposure prophylaxis (PrEP). Integrating longitudinal PrEP care into SHCs can overburden clinics. We implemented an SHC PrEP program that task shifted most PrEP operations to nonmedical staff, disease intervention specialists (DIS).

METHODS

We conducted a retrospective cohort analysis of PrEP patients in an SHC in Seattle, WA, from 2014 to 2020 to assess the number of patients served and factors associated with PrEP discontinuation. Clinicians provide same-day PrEP prescriptions, whereas DIS coordinate the program, act as navigators, and provide most follow-up care.

RESULTS

Between 2014 and 2019, 1387 patients attended an initial PrEP visit, 93% of whom were men who have sex with men. The number of patients initiating PrEP per quarter year increased from 20 to 81. The number of PrEP starts doubled when the clinic shifted from PrEP initiation at scheduled visits to initiation integrated into routine walk-in visits. The percentage of visits performed by DIS increased from 3% in 2014 to 45% in 2019. Median duration on PrEP use was 11 months. PrEP discontinuation was associated with non-Hispanic black race/ethnicity [hazard ratio (HR) 1.34, 95% confidence interval (CI) 1.02 to 1.76], age <20 years (HR 2.17, 95% CI: 1.26 to 3.75), age between 20 and 29 years (HR 1.55, 95% CI: 1.06 to 2.28), and methamphetamine use (HR 1.98, 95% CI: 1.57 to 2.49). The clinic had 750 patients on PrEP in the final quarter of 2019.

CONCLUSIONS

A demedicalized SHC PrEP model that task shifts most operations to DIS can provide PrEP at scale to high priority populations.

Tenofovir-Diphosphate in Dried Blood Spots vs Tenofovir in Urine/Plasma for Oral Preexposure Prophylaxis Adherence Monitoring

Background

Tenofovir-diphosphate (TFV-DP) measured in dried blood spots (DBS) and tenofovir (TFV) measured in urine/plasma have been used to measure TFV-based oral pre-exposure prophylaxis (PrEP) adherence. However, there are limited data comparing these 3 metrics and their appropriate use for PrEP adherence monitoring.

Methods

We collected DBS, urine, and plasma samples from HIV-negative adults randomized to a low (2 doses/week), moderate (4 doses/week), or perfect (7 doses/week) adherence group (via directly observed therapy) of tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) for 6 weeks, followed by a 4-week washout phase. Drug concentrations were measured using liquid chromatography tandem mass spectrometry. Linear mixed-effects modeling was used to examine associations between drug concentrations and dosing time.

Results

Among 28 participants, the median age was 33 years, and 12 (43%) were female. At steady state, 25th percentile TFV-DP concentrations were 466, 779, and 1375 fmol/3 mm punch in the low, moderate, and perfect adherence group, respectively. Correlation was stronger between quantifiable TFV-DP and plasma TFV (r = 0.65; P < .01) than between TFV-DP and urine TFV (r = 0.50; P < .01). Among all participants, each additional week of cumulative dosing on average led to a mean increase of 158 fmol/3 mm punch (P < .001) in TFV-DP during the dosing phase. Each additional day after the last dose was associated with 43 fmol/3 mm punch lower TFV-DP (P = .07).

Conclusions

TFV-DP levels in DBS provide valuable insight into both dosing recency and cumulative doses from variable adherence patterns. Our observed benchmark TFV-DP concentrations were slightly higher than prior predicted estimates based on convenience samples.

A multi-country cross-sectional study to assess predictors of daily versus on-demand oral pre-exposure prophylaxis in youth from South Africa, Uganda and Zimbabwe

INTRODUCTION

Sub-Saharan Africa (SSA) carries the burden of the HIV epidemic, especially among adolescents and young people (AYP). Little is known about pre-exposure prophylaxis (PrEP) uptake and preferences among AYP in SSA. We describe preferences for daily and on-demand PrEP among AYP in South Africa, Uganda and Zimbabwe.

METHODS

A cross-sectional survey was conducted in 2019 among 13- to 24-year olds, capturing socio-demographics, HIV risk behaviours and preferences for daily or on-demand PrEP. Logistic regression models were used to estimate odds ratios, adjusting for site, sex and age.

RESULTS AND DISCUSSION

A total of 1330 participants from Cape Town (n = 239), Johannesburg (n = 200), Entebbe (n = 491) and Chitungwiza (n = 400) were enrolled; 673 (51%) were male, and the median age was 19 years (interquartile range 17-22 years). Of 1287 participants expressing a preference, 60% indicated a preference for on-demand PrEP with differences by site (p < 0.001), sex (p < 0.001) and age group (p = 0.003). On-demand PrEP was most preferred in Entebbe (75%), among males (65%) versus females (54%) and in older participants (62% in 18- to 24-year-olds vs. 47% in 13- to 15-year-olds). After adjusting for site, sex and age group, preference for on-demand PrEP decreased as sex frequency over the past month increased (p-trend = 0.004) and varied with the number of partners in the last 6 months, being least popular among those reporting four or more partners (p = 0.02). Participants knowing further in advance that they were likely to have sex were more likely to prefer on-demand PrEP (p-trend = 0.02). Participants having a larger age gap with their most recent partner and participants whose last partner was a transactional sex partner or client were both less likely to prefer on-demand compared to daily PrEP (p = 0.05 and p = 0.09, respectively). Participants who knew their most recent partner was living with HIV or who did not know the HIV status of their most recent partner were less likely to prefer on-demand PrEP (p = 0.05).

CONCLUSIONS

Our data show that AYP in four SSA communities prefer on-demand over daily PrEP options, with differences seen by site, age and sex. PrEP demand creation needs to be reviewed, optimized and tailored to socio-demographic differences and designed in conjunction with AYP.

Risks and benefits of oral HIV pre-exposure prophylaxis for people with chronic hepatitis B

Individuals with chronic hepatitis B virus (HBV) infection who are at substantial risk of HIV acquisition benefit from pre-exposure prophylaxis (PrEP) with tenofovir-based antiviral therapy. Considering that tenofovir potently inhibits HBV, providing PrEP to individuals with HBV effectively results in treatment of their HBV infection. However, some clinicians might be hesitant to initiate PrEP in people with chronic HBV due to unknown risks of HBV reactivation, hepatitis, and acute liver failure during periods of antiviral cessation. Unfortunately, these knowledge gaps affect scale up of PrEP among people with chronic HBV. Emerging data regarding the risks and benefits of antiviral cessation in people with chronic HBV suggest that PrEP can be safely initiated despite the risks of non-adherence or discontinuation. People with chronic HBV who stop PrEP should be closely monitored for HBV reactivation and hepatitis flares after antiviral cessation.

Is non-occupational HIV Post Exposure Prophylaxis (nPEP) still used? An exploration of nPEP use since widespread availability of HIV PrEP

BACKGROUND

Non-occupational Post-Exposure Prophylaxis (nPEP) is an effective HIV prevention strategy in gay and bisexual men (GBM) taken after possible exposure. HIV Pre-Exposure Prophylaxis (PrEP) is also a highly effective HIV prevention strategy.

METHODS

A retrospective audit of medical records of GBM presenting to a sexual health centre and provided with nPEP compared two periods to determine if nPEP usage changed following availability of PrEP. In the first period (P1) PrEP was available through extended trials. In the second period (P2) PrEP became more accessible through the Australian Pharmaceutical Benefits Scheme (PBS). Period comparisons were performed using a two-population test of proportions with one-tailed testing and significance set at P < .05 using SPSS Statistics Version 25.

RESULTS

There were 232 GBM provided with nPEP in P1, and 202 in P2. A two-population test of proportions demonstrated that GBM presentations for nPEP decreased significantly from 302/4779 (6.3%) of GBM visits in P1 to 221/7205 (3.1%) in P2 when PrEP was more accessible (Z=8.53, P < .001). PrEP uptake after presenting for nPEP increased from 30 (12.9%) of total GBM visits in P1 to 69 (34.2%) in P2 (Z=5.26, p < .001).

CONCLUSIONS

GBM accessing nPEP decreased with statistical significance post introduction of PBS PrEP.

Texting Lost-to-follow-up PrEP Patients from a San Francisco Sexual Health Clinic

It is critical to understand what happens when PrEP patients are lost-to-follow-up (LTFU) and, where appropriate, attempt to re-engage them in care with the goal of preventing future human immunodeficiency virus (HIV) acquisition. We evaluated the benefits and limitations of using text-based outreach to re-engage with LTFU PrEP patients and offer re-initiation of PrEP care. Using text-messaging, we surveyed San Francisco City Clinic patients who started PrEP from January 2015 to October 2019 and were LTFU by October 1, 2020. Our goals were to better understand (1) whether our patients remained on PrEP through another provider or source, (2) why patients choose to discontinue PrEP, and (3) whether text-based outreach could successfully re-engage such patients in care. Multiple-choice survey questions were analyzed quantitatively to determine the proportion of respondents selecting each option; free-text responses were analyzed qualitatively using an inductive approach to identify any additional recurring themes. Of 846 eligible survey recipients, 130 responded (overall response rate 15.4%). Forty-two respondents (32.3%) were still on PrEP through another provider while 88 (67.7%) were not. Common reasons for stopping PrEP included: COVID-19–related changes in sex life (32.3% of responses), concerns regarding side effects (17.7%), and the need to take a daily pill (8.3%). Free text responses revealed additional concerns regarding risk compensation. While 32 participants agreed to be contacted by City clinic staff for PrEP counseling, only 6 were reached by phone and none of the six subsequently restarted PrEP. We learned that text messaging is a possible approach to survey certain PrEP program participants to determine who is truly LTFU and off PrEP, and to better understand reasons for PrEP discontinuation. While such information could prove valuable as programs seek to address barriers to PrEP retention, efforts to improve acceptability and increase response rates would be necessary. We were less successful in re-engaging LTFU patients in PrEP care, suggesting that text-messaging may not be the optimal strategy for this purpose.

Safety of oral tenofovir disoproxil - emtricitabine for HIV preexposure prophylaxis in adults

PURPOSE OF REVIEW

This review focuses on the safety of oral tenofovir disoproxil and emtricitabine (FTC) combination for HIV preexposure prophylaxis (PrEP) in adults.

RECENT FINDINGS

Gastrointestinal adverse events are common after treatment initiation but usually resolve within weeks. Although clinical trials did not report an increased risk of serious renal adverse events or tubulopathy, meta-analyses suggest that tenofovir disoproxil -FTC is associated with a slight but non-clinically relevant decline in estimated glomerular filtration rate (eGFR). A decline to less than 60 mL/min remains a rare event, which mainly occurs in users with an age >50 years or a baseline creatinine clearance < 90 mL/min. Similarly, a slight reduction in bone mineral density (BMD) was observed in clinical trials, but it did not result in an increased risk of bone fracture. BMD reduction and eGFR decline tend to resolve after treatment discontinuation. No drug interaction with contraception has been reported in women and no safety signal emerged in pregnant and breastfeeding women.

SUMMARY

Oral tenofovir disoproxil-FTC for HIV PrEP appears safe and well tolerated for most individuals. This supports demedicalization strategies aiming at increasing the number of PrEP users.

How could HIV-1 drug resistance impact preexposure prophylaxis for HIV prevention?

PURPOSE OF REVIEW

To review current laboratory and clinical data on the frequency and relative risk of drug resistance and range of mutations selected from approved and investigational antiretroviral agents used for preexposure prophylaxis (PrEP) of HIV-1 infection, including tenofovir disproxil fumarate (TDF)-based oral PrEP, dapivirine ring, injectable cabotegravir (CAB), islatravir, lenacapavir and broadly neutralizing antibodies (bNAbs).

RECENT FINDINGS

The greatest risk of HIV-1 resistance from PrEP with oral TDF/emtricitabine (FTC) or injectable CAB is from starting or continuing PrEP after undiagnosed acute HIV infection. By contrast, the dapivirine intravaginal ring does not appear to select nonnucleoside reverse transcriptase inhibitor resistance in clinical trial settings. Investigational inhibitors including islatravir, lenacapavir, and bNAbs are promising for use as PrEP due to their potential for sustained delivery and low risk of cross-resistance to currently used antiretrovirals, but surveillance for emergence of resistance mutations in more HIV-1 gene regions (gag, env) will be important as the same drugs are being developed for HIV therapy.

SUMMARY

PrEP is highly effective in preventing HIV infection. Although HIV drug resistance from PrEP use could impact future options in individuals who seroconvert on PrEP, the current risk is low and continued monitoring for the emergence of resistance and cross-resistance during product development, clinical studies, and product roll-out is advised to preserve antiretroviral efficacy for both treatment and prevention.

The Cost-Effectiveness of HIV/STI Prevention in High-Income Countries with Concentrated Epidemic Settings: A Scoping Review

The purpose of this scoping review is to establish the state of the art on economic evaluations in the field of HIV/STI prevention in high-income countries with concentrated epidemic settings and to assess what we know about the cost-effectiveness of different measures. We reviewed economic evaluations of HIV/STI prevention measures published in the Web of Science and Cost-Effectiveness Registry databases. We included a total of 157 studies focusing on structural, behavioural, and biomedical interventions, covering a variety of contexts, target populations and approaches. The majority of studies are based on mathematical modelling and demonstrate that the preventive measures under scrutiny are cost-effective. Interventions targeted at high-risk populations yield the most favourable results. The generalisability and transferability of the study results are limited due to the heterogeneity of the populations, settings and methods involved. Furthermore, the results depend heavily on modelling assumptions. Since evidence is unequally distributed, we discuss implications for future research.