HIV prevention strategies and risk of infection: a model-based analysis

PrEP for women in Europe: a systematic literature review

BACKGROUND

Prevention of HIV transmission is fundamental to ending the HIV epidemic. Pre-exposure prophylaxis (PrEP) with oral tenofovir-emtricitabine (TDF-FTC) is an established HIV-prevention method; however, most PrEP services in Europe have been targeted at men who have sex with men (MSM). A survey in 2021 by Women Against Viruses in Europe (WAVE) showed considerable variation in PrEP access and guidance for women throughout Europe. WAVE therefore commissioned this systematic review to provide insight into PrEP provision and barriers to uptake for women in Europe.

METHODS

PubMed, Embase, and Scopus were searched for studies (January 2013-May 2021) that reported on actual (e.g., efficacy and safety) or hypothetical (e.g., awareness, barriers, PrEP impact models) use of oral PrEP involving women (including cis, transgender, pregnant, migrant, and breastfeeding women). Search terms included HIV, pre-exposure prophylaxis (specifically TDF-FTC), and women. Studies performed outside of the World Health Organization European region were excluded.

RESULTS

The search identified 4716 unique citations, and 45 peer-reviewed articles (44 studies) were included. The majority of these studies (34/44 [77%]) included recipients or potential recipients of PrEP, representing 4699 women (243 transgender women). However, few studies were women focused (4/34 [12%]) or took place outside of Western Europe (3/34 [9%]). Across the three clinical studies that reported women-specific outcomes (60 transgender women, 13 pregnant, and 19 cis women), no breakthrough infections were recorded during the use of PrEP. Lack of awareness of PrEP, low self-estimation of HIV acquisition risk, concerns about stigma, lack of protection against other sexually transmitted infections, and PrEP interaction with hormones (for transgender women) were identified as barriers to use. The remaining studies examined healthcare professionals' perceptions of PrEP (9/44 [20%]), asked for public opinion (2/44 [5%]), or modelled the potential of PrEP for HIV prevention (1/44 [2%]).

CONCLUSIONS

This review revealed a notable lack of literature on PrEP for cis and transgender women in Europe. This is synonymous with a lack of PrEP provision for women in this region. Barriers to PrEP uptake are complex and rooted in institutional and societal stigma, which must be addressed at policy level. HIV prevention with PrEP is not 'one size fits all' and requires a nuanced gender-responsive approach. Further research into the use of PrEP in cis, pregnant, breastfeeding, and transgender women is essential if we are to stop HIV transmission by 2030.

Optimization of Case Definitions for Sensitivity as a Preventive Strategy-A Modelling Exemplified with Rapid Diagnostic Test-Based Prevention of Sexual HIV Transmission

In clinical studies, case definitions are usually designed to optimally match the desired clinical state, because lacking specificity is associated with a risk of bias regarding the study outcome. In preventive medicine, however, high sensitivity is sometimes considered as more critical in order not to overlook infectious individuals, because the latter may be associated with ongoing spread of a transmittable disease. Accordingly, this work was focused on a theoretical model on how the sensitivity of case definitions can be optimized by adding clinical symptoms to diagnostic results for preventive purposes, if the associated reduction in specificity is considered as acceptable. The model was exemplified with an analysis on whether and in how far exposure risk can be reduced by the inclusion of observable symptoms during seroconversion syndrome in case of rapid diagnostic test-based prevention of sexual HIV transmission. The approach provided a high level of safety (negative predictive values close to 1) for the price of a considerably number of false positives (positive predictive values < 0.01 for some subpopulations). When applying such a sensitivity-optimized screening as a "diagnostics as prevention" strategy, the advantages of excellent negative predictive values need to be cautiously balanced against potential undesirable consequences of low positive predictive values.

Social Network Interventions for HIV Transmission Elimination

Purpose of Review

Network interventions for HIV prevention represent a potential area for growth in a globalizing world, where persons are more easily connected to one another through social media and networking applications. The basic tenets of network interventions such as (1) selection of a change agent, (2) segmentation, (3) induction, and (4) alteration represent myriad ways to structure network interventions for HIV prevention with the potential for large public health impact.

Recent Findings

Recent studies have employed the use of social networking websites such as Facebook to identify key persons to recruit others and disseminate information aimed at decreasing HIV transmission and improving safe sex practices among groups who are more vulnerable to HIV acquisition. Many of these interventions have successfully decreased HIV risk behaviors as well as decreased the spread of HIV among intervention cohorts.

Summary

Network interventions for HIV prevention provide more opportunities to reach populations who have not been reached through typical efforts employed in clinical and public health settings, though they are not currently widely employed by the public health community and other stakeholders.

Evaluation of the Xiamen AmonMed Biotechnology rapid diagnostic test COVID-19 IgM/IgG test kit (Colloidal gold)

Introduction

To efficiently monitor the COVID-19 pandemic for surveillance purposes, reliable serological rapid diagnostic tests (RDTs) are desirable for settings where well-established high-throughput bench-top solutions are not available. Here, we have evaluated such an RDT.

Methods

We have assessed the Xiamen AmonMed Biotechnology COVID-19 IgM/IgG test kit (Colloidal gold) and the EUROIMMUN benchtop assay with serum samples from patients with polymerase chain reaction (PCR)-confirmed COVID-19 disease. Samples from patients with Epstein-Barr-virus (EBV) infection and blood donors were used for specificity testing.

Results

For the colloid gold rapid test and the EUROIMMUN assay, the study indicated overall sensitivity of 15.2% and 67.4%, respectively, while specificity of 99.0% and 97.9% with the blood donor sera, as well as 100% and 96.8% with the EBV-patients, were observed, respectively. An association of the time period between positive PCR results and serum acquisition with serological test positivity could be observed for the immunologlobulin G subclass of the EUROIMMUN assay only.

Conclusions

In spite of acceptable specificity of the assessed RDT, the detected poor sensitivity leaves room for improvement. The test results remain difficult to interpret and therefore the RDT can currently not be recommended for routine diagnostic or surveillance use.

Comparison of Self-Reported Sexual Activity Among Heterosexuals with Sexual Spread of Poorly Transmittable Agents: A Minimalistic Approach to Estimating Sexual Activity Based on HIV Incidence

The aim of this study was to assess whether epidemics of sexually transmitted infections caused by poorly transmittable agents corresponded to self-reported sexual activity in a distinct population. To exemplify this, a model was used to investigate whether HIV infection incidences corresponded to the extent of sexual activity as assessed by a questionnaire-based study. The model suggested between 97 and 486 sexual contacts per German individual during a sexually active lifetime based on the annual HIV incidence of 680 among the heterosexual population reported by the German National Health Authority. This is in line with the estimated 296 sexual contacts during one's lifetime, which was indicated by questionnaire respondents. The model confirms the correspondence of self-reported sexual activity with HIV incidence as reported by the German National Health Authority. Accordingly, HIV incidence- and prevalence-based modeling of sexual activity in a population provides crude estimations in situations where a range of uncertainty is acceptable. The model's veracity is limited by a number of assumptions necessitated by the paucity of data. Nevertheless, the model may be suitable in settings where severe reporting bias has to be expected for legal or socio-cultural reasons.

Sexually Transmitted Infections in Soldiers - A Cross-Sectional Assessment in German Paratroopers and Navy Soldiers and a Literature Review

Introduction

The study was performed to estimate the prevalence and determinants of occurrence of sexually transmitted infections (STIs) in paratroopers and navy soldiers by anonymously analyzing medical records from the medical departments of two large German barracks in order to assess the need for medical STI prevention.

Methods

Medical records from 80 paratroopers and 80 navy soldiers were screened for records of STI. Results were anonymously collected next to information on risk factors, as well as diagnostic and therapeutic management, and comparatively assessed.

Results

Proportions of suspected STIs were 17.5% and 20%, and proportions of diagnosed STIs were 13.9% and 11.3% for paratroopers and navy soldiers, respectively. Chlamydia trachomatis, human papillomavirus, and genital scabies were observed in paratroopers and navy soldiers, while Gardnerella vaginalis, herpes simplex virus, Molluscum contagiosum virus, Neisseria gonorrhoeae, and Trichomonas vaginalis were additionally identified in navy soldiers.

Conclusions

Although clinical hints for STIs were frequently observed, clinical management was usually restricted to syndrome-based antibiotic treatment without detailed diagnostic workup, leaving room for procedural improvement. Ongoing need for medical STI prevention in the military could be confirmed.

Diagnostics as Prevention - A Rapid Testing-Based Strategy of Sex Workers against Sexual HIV Exposure

Introduction

German sex workers have illegally established a prevention strategy, which consists of testing potential sexual partners with human immunodeficiency virus (HIV)-specific rapid diagnostic tests (RDTs) prior to engaging in unprotected sexual intercourse eventually performed in case of a negative test result. Based on a recently established modeling approach, the effectiveness of this strategy regarding the risk of HIV exposure was compared with protection provided by condom use.

Methods

Based on a literature search, the following assumptions were used for the calculations: an averaged 80% exposure risk reduction with a condom used during sexual intercourse, usage of a well-characterized 4th-generation HIV RDT, and a 10 day post-infection period without any measurable viral load in peripheral blood followed by a sero-conversion period of about 3 weeks with 12.3% test sensitivity (antigen-specific) and only afterwards 97.3% (antibody-specific) test sensitivity.

Results

In most constellations, the HIV exposure risk in case of RDT-based prevention was lower than with condom use. Conclusions: The RDT-based HIV exposure prevention as established by sex workers is effective in most situations. A notable weakness of the strategy is the RDTs' poor sensitivity in spite of a high transmission risk during the seroconversion stage.