Minimal impact of circumcision on HIV acquisition in men who have sex with men

Does Voluntary Medical Male Circumcision Reduce HIV Risk in Men Who Have Sex with Men?

PURPOSE OF REVIEW

To review the evidence on the effect of voluntary medical male circumcision (VMMC) on reducing HIV risk among men who have sex with men (MSM) and assess the limitations of available evidence.

RECENT FINDINGS

Individual studies have shown conflicting results, but recent meta-analyses have consistently suggested that VMMC was associated with 7 to 23% reductions in HIV prevalence or incidence in MSM, particularly among a subgroup of men who predominantly practice insertive role in anal sex. Mathematical models have also suggested a moderate population-level impact of VMMC intervention. All original studies have been observational and are subject to confounding and bias. Randomized clinical trials (RCTs) are needed to provide strong evidence of assessing the efficacy of VMMC on HIV risk among MSM. VMMC is a promising HIV risk reduction tool for MSM. RCTs are needed to evaluate the efficacy of VMMC intervention.

Predicting the long-term impact of voluntary medical male circumcision on HIV incidence among men who have sex with men in Beijing, China

Using a deterministic compartmental modeling procedure to fit prevalence from 2005-2015, we projected new HIV cases during 2016-2026 under different coverage rates ranging from 0.0001 (at baseline) to 0.15 (an optimistic assumption) with simulations on varying transmission rates, model calibration to match historical data, and sensitivity analyses for different assumptions. Compared with the baseline (λ = 0.0001), we found the new HIV cases would reduce with the increase of coverage rates of the voluntary medical male circumcision (VMMC) among men who have sex wtih men (MSM). The higher the coverage rate, the lower the new HIV incidence would be. As one of the first studies to model the potential impact of VMMC among MSM in China, our model suggested a modest to the significant public health impact of VMMC. Even at just 15% VMMC annual uptake rate, the reduction in new infections is substantial. Therefore, there is a strong need to determine the efficacy of VMMC among MSM, to improve the evidence base for its potential use among MSM in low circumcision settings. Only then can policymakers decide whether to incorporate VMMC into a package of HIV prevention interventions targeting MSM.

The changing molecular epidemiology of HIV in the Philippines

BACKGROUND

The Philippines has one of the fastest-growing HIV epidemics in the world. Possible reasons for this include increased testing, increased local transmission, and possibly more aggressive strains of HIV. This study sought to determine whether local molecular subtypes of HIV have changed.

METHODS

Viruses from 81 newly diagnosed, treatment-naive HIV patients were genotyped using protease and reverse transcriptase genes. Demographic characteristics and CD4 count data were collected.

RESULTS

The cohort had an average age of 29 years (range 19-51 years), CD4+ count of 255 cells/mm³ (range 2-744 cells/mm³), and self-reported acquisition time of 2.42 years (range 0.17-8.17 years). All were male, including 79 men who have sex with men (MSM). The genotype distribution was 77% CRF01_AE, 22% B, and 1% C. Previous data from 1985-2000 showed that most Philippine HIV infections were caused by subtype B (71%, n=100), followed by subtype CRF01_AE (20%). Comparison with the present cohort showed a significant shift in subtype (p<0.0001). Comparison between CRF01_AE and B showed a lower CD4+ count (230 vs. 350 cells/mm³, p=0.03). Survival data showed highly significant survival associated with antiretroviral (ARV) treatment (p<0.0001), but no significant difference in mortality or CD4 count increase on ARVs between subtypes.

CONCLUSIONS

The molecular epidemiology of HIV in the Philippines has changed, with the more aggressive CRF01_AE now being the predominant subtype.

Lower HIV Risk Among Circumcised Men Who Have Sex With Men in China: Interaction With Anal Sex Role in a Cross-Sectional Study

BACKGROUND

Voluntary medical male circumcision reduces the risk of HIV heterosexual transmission in men, but its effect on male-to-male sexual transmission is uncertain.

METHODS

Circumcision status of men who have sex with men (MSM) in China was evaluated by genital examination and self-report; anal sexual role was assessed by questionnaire interview. Serostatus for HIV and syphilis was confirmed.

RESULTS

Among 1155 participants (242 were seropositive and 913 with unknown HIV status at enrollment), the circumcision rate by self-report (10.4%) was higher than confirmed by genital examination (8.2%). Male circumcision (by examination) was associated with 47% lower odds of being HIV seropositive [adjusted odds ratio (aOR): 0.53; 95% confidence interval (CI): 0.27 to 1.02] after adjusting for demographic covariates, number of lifetime male sexual partners, and anal sex role. Among MSM who predominantly practiced insertive anal sex, circumcised men had 62% lower odds of HIV infection than those who were uncircumcised (aOR: 0.38; 95% CI: 0.09 to 1.64). Among those whose anal sex position was predominantly receptive or versatile, circumcised men have 46% lower odds of HIV infection than did men who were not circumcised (aOR: 0.54; 95% CI: 0.25 to 1.14). Compared to uncircumcised men reporting versatile or predominantly receptive anal sex positioning, those who were circumcised and reported practicing insertive sex had an 85% lower risk (aOR: 0.15; 95% CI: 0.04 to 0.65). Circumcision was not associated clearly with lower syphilis risk (aOR: 0.91; 95% CI: 0.51 to 1.61).

CONCLUSIONS

Circumcised MSM were less likely to have acquired HIV, most pronounced among men predominantly practicing insertive anal intercourse. A clinical trial is needed.

Can male circumcision have an impact on the HIV epidemic in men who have sex with men?

BACKGROUND

Three trials have demonstrated the prophylactic effect of male circumcision (MC) for HIV acquisition among heterosexuals, and MC interventions are underway throughout sub-Saharan Africa. Similar efforts for men who have sex with men (MSM) are stymied by the potential for circumcised MSM to acquire HIV easily through receptive sex and transmit easily through insertive sex. Existing work suggests that MC for MSM should reach its maximum potential in settings where sexual role segregation is historically high and relatively stable across the lifecourse; HIV incidence among MSM is high; reported willingness for prophylactic circumcision is high; and pre-existing circumcision rates are low. We aim to identify the likely public health impact that MC interventions among MSM would have in one setting that fulfills these conditions-Peru-as a theoretical upper bound for their effectiveness among MSM generally.

METHODS AND FINDINGS

We use a dynamic, stochastic sexual network model based in exponential-family random graph modeling and parameterized from multiple behavioral surveys of Peruvian MSM. We consider three enrollment criteria (insertive during 100%, >80% or >60% of UAI) and two levels of uptake (25% and 50% of eligible men); we explore sexual role proportions from two studies and different frequencies of switching among role categories. Each scenario is simulated 10 times. We estimate that efficiency could reach one case averted per 6 circumcisions. However, the population-level impact of an optimistic MSM-MC intervention in this setting would likely be at most ∼5-10% incidence and prevalence reductions over 25 years.

CONCLUSIONS

Roll-out of MC for MSM in Peru would not result in a substantial reduction in new HIV infections, despite characteristics in this population that could maximize such effects. Additional studies are needed to confirm these results for other MSM populations, and providers may consider the individual health benefits of offering MC to their MSM patients.

Mathematical models for the study of HIV spread and control amongst men who have sex with men

For a quarter of century, mathematical models have been used to study the spread and control of HIV amongst men who have sex with men (MSM). We searched MEDLINE and EMBASE databases up to the end of 2010 and reviewed this literature to summarise the methodologies used, key model developments, and the recommended strategies for HIV control amongst MSM. Of 742 studies identified, 127 studies met the inclusion criteria. Most studies employed deterministic modelling methods (80%). Over time we saw an increase in model complexity regarding antiretroviral therapy (ART), and a corresponding decrease in complexity regarding sexual behaviours. Formal estimation of model parameters was carried out in only a small proportion of the studies (22%) while model validation was considered by an even smaller proportion (17%), somewhat reducing confidence in the findings from the studies. Nonetheless, a number of common conclusions emerged, including (1) identification of the importance of assumptions regarding changes in infectivity and sexual contact rates on the impact of ART on HIV incidence, that subsequently led to empirical studies to gather these data, and (2) recommendation that multiple strategies would be required for effective HIV control amongst MSM. The role of mathematical models in studying epidemics is clear, and the lack of formal inference and validation highlights the need for further developments in this area. Improved methodologies for parameter estimation and systematic sensitivity analysis will help generate predictions that more fully express uncertainty, allowing better informed decision making in public health.

Expected epidemiological impact of the introduction of a partially effective HIV vaccine among men who have sex with men in Australia

A trial of the ALVAC-AIDSVAX HIV vaccine was recently found to be partially effective in preventing HIV transmission among study participants in Thailand. The success of this trial means that vaccination may become a viable intervention for the prevention of HIV infection in the medium-term future. Assuming that the vaccine has similar relative protective effectiveness per exposure event for reducing transmission among men who have sex with men (MSM) in high-income settings we investigated the potential population-level impact of rolling out such a vaccine among MSM in New South Wales, Australia. Using a detailed individual-based transmission model that simulates a population of sexually active MSM it was found that one-off intervention of 60% or 30% coverage of a vaccine with characteristics like the ALVAX-AIDSVAX vaccine would likely reduce the cumulative incidence of HIV by 9.6% and 5.1%, respectively, over a 10-year period. Due to the waning of vaccine efficacy, a booster vaccination could be required to maintain this reduction in incidence over the long term. If the previously vaccinated population is given a booster vaccine, with the same protection conferred as with the initial vaccination, every 5 years or every 2 years then the cumulative incidence over 10 years for 60% coverage could be reduced by 14.4% and 22.8%, respectively. Such a weak vaccine, with boosting, may be a potential intervention strategy for the prevention of HIV infection in MSM in high-income countries if further trials show boosting to be safe, acceptable, and cost-effective. However, the moderately low population-level impact suggests that a public health strategy involving such a vaccine should be supplemented with other biomedical and educational strategies.