HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention
01 Aug 2010-International Journal of Epidemiology (Oxford University Press)-Vol. 39, Iss: 4, pp 1048-1063
TL;DR: It was demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time.
Abstract: Background The human immunodeficiency virus (HIV) infectiousness of anal intercourse (AI) has not been systematically reviewed, despite its role driving HIV epidemics among men who have sex with men (MSM) and its potential contribution to heterosexual spread. We assessed the per-act and per-partner HIV transmission risk from AI exposure for heterosexuals and MSM and its implications for HIV prevention.
Methods Systematic review and meta-analysis of the literature on HIV-1 infectiousness through AI was conducted. PubMed was searched to September 2008. A binomial model explored the individual risk of HIV infection with and without highly active antiretroviral therapy (HAART).
Results A total of 62 643 titles were searched; four publications reporting per-act and 12 reporting per-partner transmission estimates were included. Overall, random effects model summary estimates were 1.4% [95% confidence interval (CI) 0.2–2.5)] and 40.4% (95% CI 6.0–74.9) for per-act and per-partner unprotected receptive AI (URAI), respectively. There was no significant difference between per-act risks of URAI for heterosexuals and MSM. Per-partner unprotected insertive AI (UIAI) and combined URAI–UIAI risk were 21.7% (95% CI 0.2–43.3) and 39.9% (95% CI 22.5–57.4), respectively, with no available per-act estimates. Per-partner combined URAI–UIAI summary estimates, which adjusted for additional exposures other than AI with a ‘main’ partner [7.9% (95% CI 1.2–14.5)], were lower than crude (unadjusted) estimates [48.1% (95% CI 35.3–60.8)]. Our modelling demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time. AI may substantially increase HIV transmission risk even if the infected partner is receiving HAART; however, predictions are highly sensitive to infectiousness assumptions based on viral load.
Conclusions Unprotected AI is a high-risk practice for HIV transmission, probably with substantial variation in infectiousness. The significant heterogeneity between infectiousness estimates means that pooled AI HIV transmission probabilities should be used with caution. Recent reported rises in AI among heterosexuals suggest a greater understanding of the role AI plays in heterosexual sex lives may be increasingly important for HIV prevention.
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TL;DR: In Kenya, men who have sex with men (MSM) are increasingly using virtual sites, including web‐based apps, to meet sex partners, and HIV testing, HIV prevalence, awareness of HIV‐positive status and linkage to antiretroviral therapy (ART) are examined.
Abstract: INTRODUCTION In Kenya, men who have sex with men (MSM) are increasingly using virtual sites, including web-based apps, to meet sex partners We examined HIV testing, HIV prevalence, awareness of HIV-positive status and linkage to antiretroviral therapy (ART), for HIV-positive MSM who solely met partners via physical sites (PMSM), compared with those who did so in virtual sites (either solely via virtual sites (VMSM), or via both virtual and physical sites (DMSM)) METHODS We conducted a cross-sectional bio-behavioural survey of 1200 MSM, 15 years and above, in three counties in Kenya between May and July 2019, using random sampling of physical and virtual sites We classified participants as PMSM, DMSM and VMSM, based on where they met sex partners, and compared the following between groups using chi-square tests: (i) proportion tested; (ii) HIV prevalence and (iii) HIV care continuum among MSM living with HIV We then performed multivariable logistic regression to measure independent associations between network engagement and HIV status RESULTS 177 (147%), 768 (640%) and 255 (212%), of participants were classified as PMSM, DMSM and VMSM respectively 684%, 704% and 785% of PMSM, DMSM and VMSM, respectively, reported an HIV test in the previous six months HIV prevalence was 85% (PMSM), 154% (DMSM) and 267% (VMSM), p < 0001 Among those living with HIV, 467% (PMSM), 415% (DMSM) and 294% (VMSM) were diagnosed and aware of their status; and 400%, 356% and 265% were on antiretroviral treatment After adjustment for other predictors, MSM engaged in virtual networks remained at a two to threefold higher risk of prevalent HIV: VMSM versus PMSM (adjusted odds ratio 388 (95% confidence interval (CI) 184 to 817) p < 0001); DMSM versus PMSM (200 (95% CI 103 to 387), p = 0040) CONCLUSIONS Engagement in virtual networks is associated with elevated HIV risk, irrespective of individual-level risk factors Understanding the difference in characteristics among MSM-seeking partners in different sites will help HIV programmes to develop subpopulation-specific interventions
15 citations
Cites background or methods from "HIV transmission risk through anal ..."
...We then sought to estimate the independent risk of HIV by network type, after accounting for individual-level predictors of prevalent HIV infection among MSM in Kenya [19-22]....
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...We adjusted for county and for potential individual-level confounders for prevalent HIV infection based on prior literature [19-22]: socio-demographic characteristics (age, educational attainment); and sexual behaviour and partnership characteristics....
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TL;DR: Evaluation of the likelihood that a UK man who has sex with men (MSM) would be exposed to PrEP‐resistant HIV in a homosexual encounter with an HIV‐infectious partner found PrEP efficacy to be compromised if the challenge virus is antiretroviral therapy (ART)‐resistant.
Abstract: Objectives
Recent studies have shown that pre-exposure prophylaxis (PrEP) can substantially reduce the chance of acquiring HIV infection. However, PrEP efficacy has been found to be compromised in macaque studies if the challenge virus is antiretroviral therapy (ART)-resistant. Our objective was to evaluate the likelihood that a UK man who has sex with men (MSM) would be exposed to PrEP-resistant HIV in a homosexual encounter with an HIV-infectious partner.
Methods
Data from the UK Collaborative HIV Cohort (UK CHIC) study were linked to the UK HIV Drug Resistance Database for HIV-1-positive MSM patients seen between 2005 and 2008. Patients were categorized as undiagnosed; diagnosed but ART-naive; ART-experienced and on treatment; and ART-experienced and on a treatment interruption. Considering current PrEP regimens, resistance to (a) tenofovir (TDF) alone, (b) TDF and emtricitabine (FTC), and (c) TDF or FTC was estimated. Patients without resistance tests had PrEP resistance imputed using bootstrapping and logistic regression models.
Results
The population-level prevalence of PrEP resistance in HIV-infectious individuals in 2008 was estimated to be 1.6, 0.9 and 4.1% for PrEP resistance definitions a, b and c, respectively. Prevalence in ART-experienced patients was highest, with negligible circulating resistance amongst ART-naive individuals. The levels of resistance declined over the period of study.
Conclusions
Our analysis indicates low levels of resistance to proposed PrEP drugs. The estimated PrEP resistance prevalence in UK HIV-infected MSM is towards the lower range of values used in simulation studies which have suggested that circulating PrEP drug resistance will have a negligible impact on PrEP efficacy at the population level.
15 citations
TL;DR: An agent-based ABM of HIV in South Africa is presented, developed to characterize the key social drivers of HIVIn South Africa and the groups that are at the highest risk of HIV.
Abstract: Background: Although many mathematical models have been developed to simulate the likely effect of biomedical HIV interventions, there have been relatively few mathematical models that describe the social and structural drivers of HIV and the factors that account for heterogeneity in HIV risk within populations. This report provides a technical description of MicroCOSM, a model developed to address these issues in the South African context.
Methods: MicroCOSM is an agent-based model, which assigns to each simulated individual a number of demographic characteristics (age, sex and race) and socio-economic characteristics (educational attainment, current schooling, urban-rural location, migrancy and incarceration history). These in turn influence individual access to and uptake of healthcare (condom preference, HIV testing, hormonal contraceptive use, male circumcision, antiretroviral treatment) and sexual behaviour (sexual preference, propensity for concurrent partners and commercial sex, marital status, number of partners). All of these factors affect health outcomes (fertility, mortality, HIV and other sexually transmitted infections), which in turn dynamically influence socio-economic status, healthcare access and sexual behaviour. Individuals are linked to partners in dynamic sexual networks. The model simulates the South African population over the period from 1985 to the present.
Results: The model matches the observed levels of HIV prevalence in South Africa by age and sex, as well as the observed changes in HIV prevalence over time. The model also matches observed patterns of HIV prevalence by educational attainment, by urban-rural location and by history of recent migration. Estimates of HIV prevalence in key populations (sex workers, men who have sex with men and prisoners) are roughly consistent with surveys. The model has also been calibrated to match total numbers of HIV tests and male circumcision operations performed in South Africa, as well as estimates of HIV diagnosis and antiretroviral treatment coverage from other models.
Conclusions: MicroCOSM is a fully-integrated model of the social, biomedical and behavioural factors that drive HIV and other sexually transmitted infections in South Africa. This work lays the foundation for a more quantitative approach to understanding which sub-populations are currently at the greatest HIV risk, and to assessing what interventions are needed to reduce socioeconomic and racial inequality in health outcomes.
15 citations
Cites background from "HIV transmission risk through anal ..."
...In a systematic review of these studies, Baggaley et al [440] estimated the average transmission probability, per act of unprotected receptive anal intercourse, to be 0....
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...In a systematic review of these studies, Baggaley et al [440] estimated the average transmission probability, per act of unprotected receptive anal intercourse, to be 0.014 (95% CI: 0.002-0.025)....
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TL;DR: Although all models overestimated HIV incidence, micro-simulations with greater heterogeneity in the HIV transmission modelling process produced more robust results and better reproduced empirical epidemic dynamics.
Abstract: We investigated how different models of HIV transmission, and assumptions regarding the distribution of unprotected sex and syringe-sharing events ('risk acts'), affect quantitative understanding of HIV transmission process in people who inject drugs (PWID). The individual-based model simulated HIV transmission in a dynamic sexual and injecting network representing New York City. We constructed four HIV transmission models: model 1, constant probabilities; model 2, random number of sexual and parenteral acts; model 3, viral load individual assigned; and model 4, two groups of partnerships (low and high risk). Overall, models with less heterogeneity were more sensitive to changes in numbers risk acts, producing HIV incidence up to four times higher than that empirically observed. Although all models overestimated HIV incidence, micro-simulations with greater heterogeneity in the HIV transmission modelling process produced more robust results and better reproduced empirical epidemic dynamics.
15 citations
TL;DR: No evidence for an association between self-rated HIV prevention knowledge and taking less part in risky practices was found, suggesting knowledge-intensive interventions may not be the best fit for reducing HIV transmission.
Abstract: This study aimed to identify sub-groups of men who have sex with men at high risk of HIV infection. Data from the Swedish MSM2013 survey were analysed with a focus on respondents (n = 714) who reported having had unprotected anal intercourse with male casual partner(s) in the past 12 months. Weighted Latent Class Analysis with covariates and distal outcomes was conducted to identify sub-groups of men sharing the same sexual practice characteristics. Four latent classes emerged: experimentals, bottoms, risk-reducers and clubbers. Experimentals appeared to differ most from the other classes. They had extensive experience of barebacking, the use of poppers and fisting. Higher number of casual male sex partners and reporting having HIV were predictors for belonging to experimentals. No evidence for an association between self-rated HIV prevention knowledge and taking less part in risky practices was found. Hence, knowledge-intensive interventions may not be the best fit for reducing HIV transmission. This diversity of men based on similar sexual practice patterns should be taken into account when designing future HIV prevention interventions.
14 citations
Cites background from "HIV transmission risk through anal ..."
...The first of these identified sexual practices associated with risk for transmission of HIV, including insertive and receptive anal sex without condom and insertive and receptive oral sex without condom (Baggaley, White, and Boily 2010; Scott et al. 2014)....
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...Being the receptive partner to an HIV-positive insertive partner carries the largest transmission risk, estimated at 1.4% (95%CI: 0.2–2.5) per-act and per-partner for unprotected receptive anal intercourse (Baggaley, White, and Boily 2010)....
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...As pointed out previously, being the receptive partner to an HIV-positive insertive partner conveys the largest transmission risk (Baggaley, White, and Boily 2010)....
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References
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TL;DR: A new quantity is developed, I 2, which the authors believe gives a better measure of the consistency between trials in a meta-analysis, which is susceptible to the number of trials included in the meta- analysis.
Abstract: Cochrane Reviews have recently started including the quantity I 2 to help readers assess the consistency of the results of studies in meta-analyses. What does this new quantity mean, and why is assessment of heterogeneity so important to clinical practice?
Systematic reviews and meta-analyses can provide convincing and reliable evidence relevant to many aspects of medicine and health care.1 Their value is especially clear when the results of the studies they include show clinically important effects of similar magnitude. However, the conclusions are less clear when the included studies have differing results. In an attempt to establish whether studies are consistent, reports of meta-analyses commonly present a statistical test of heterogeneity. The test seeks to determine whether there are genuine differences underlying the results of the studies (heterogeneity), or whether the variation in findings is compatible with chance alone (homogeneity). However, the test is susceptible to the number of trials included in the meta-analysis. We have developed a new quantity, I 2, which we believe gives a better measure of the consistency between trials in a meta-analysis.
Assessment of the consistency of effects across studies is an essential part of meta-analysis. Unless we know how consistent the results of studies are, we cannot determine the generalisability of the findings of the meta-analysis. Indeed, several hierarchical systems for grading evidence state that the results of studies must be consistent or homogeneous to obtain the highest grading.2–4
Tests for heterogeneity are commonly used to decide on methods for combining studies and for concluding consistency or inconsistency of findings.5 6 But what does the test achieve in practice, and how should the resulting P values be interpreted?
A test for heterogeneity examines the null hypothesis that all studies are evaluating the same effect. The usual test statistic …
45,105 citations
TL;DR: A checklist contains specifications for reporting of meta-analyses of observational studies in epidemiology, including background, search strategy, methods, results, discussion, and conclusion should improve the usefulness ofMeta-an analyses for authors, reviewers, editors, readers, and decision makers.
Abstract: ObjectiveBecause of the pressure for timely, informed decisions in public health
and clinical practice and the explosion of information in the scientific literature,
research results must be synthesized. Meta-analyses are increasingly used
to address this problem, and they often evaluate observational studies. A
workshop was held in Atlanta, Ga, in April 1997, to examine the reporting
of meta-analyses of observational studies and to make recommendations to aid
authors, reviewers, editors, and readers.ParticipantsTwenty-seven participants were selected by a steering committee, based
on expertise in clinical practice, trials, statistics, epidemiology, social
sciences, and biomedical editing. Deliberations of the workshop were open
to other interested scientists. Funding for this activity was provided by
the Centers for Disease Control and Prevention.EvidenceWe conducted a systematic review of the published literature on the
conduct and reporting of meta-analyses in observational studies using MEDLINE,
Educational Research Information Center (ERIC), PsycLIT, and the Current Index
to Statistics. We also examined reference lists of the 32 studies retrieved
and contacted experts in the field. Participants were assigned to small-group
discussions on the subjects of bias, searching and abstracting, heterogeneity,
study categorization, and statistical methods.Consensus ProcessFrom the material presented at the workshop, the authors developed a
checklist summarizing recommendations for reporting meta-analyses of observational
studies. The checklist and supporting evidence were circulated to all conference
attendees and additional experts. All suggestions for revisions were addressed.ConclusionsThe proposed checklist contains specifications for reporting of meta-analyses
of observational studies in epidemiology, including background, search strategy,
methods, results, discussion, and conclusion. Use of the checklist should
improve the usefulness of meta-analyses for authors, reviewers, editors, readers,
and decision makers. An evaluation plan is suggested and research areas are
explored.
17,663 citations
TL;DR: The problem of making a combined estimate has been discussed previously by Cochran and Yates and Cochran (1937) for agricultural experiments, and by Bliss (1952) for bioassays in different laboratories as discussed by the authors.
Abstract: When we are trying to make the best estimate of some quantity A that is available from the research conducted to date, the problem of combining results from different experiments is encountered. The problem is often troublesome, particularly if the individual estimates were made by different workers using different procedures. This paper discusses one of the simpler aspects of the problem, in which there is sufficient uniformity of experimental methods so that the ith experiment provides an estimate xi of u, and an estimate si of the standard error of xi . The experiments may be, for example, determinations of a physical or astronomical constant by different scientists, or bioassays carried out in different laboratories, or agricultural field experiments laid out in different parts of a region. The quantity xi may be a simple mean of the observations, as in a physical determination, or the difference between the means of two treatments, as in a comparative experiment, or a median lethal dose, or a regression coefficient. The problem of making a combined estimate has been discussed previously by Cochran (1937) and Yates and Cochran (1938) for agricultural experiments, and by Bliss (1952) for bioassays in different laboratories. The last two papers give recommendations for the practical worker. My purposes in treating the subject again are to discuss it in more general terms, to take account of some recent theoretical research, and, I hope, to bring the practical recommendations to the attention of some biologists who are not acquainted with the previous papers. The basic issue with which this paper deals is as follows. The simplest method of combining estimates made in a number of different experiments is to take the arithmetic mean of the estimates. If, however, the experiments vary in size, or appear to be of different precision, the investigator may wonder whether some kind of weighted meani would be more precise. This paper gives recommendations about the kinds of weighted mean that are appropriate, the situations in which they
4,335 citations
TL;DR: The viral load is the chief predictor of the risk of heterosexual transmission of HIV-1, and transmission is rare among persons with levels of less than 1500 copies of HIV -1 RNA per milliliter.
Abstract: Background and Methods We examined the influence of viral load in relation to other risk factors for the heterosexual transmission of human immunodeficiency virus type 1 (HIV-1). In a community-based study of 15,127 persons in a rural district of Uganda, we identified 415 couples in which one partner was HIV-1–positive and one was initially HIV-1–negative and followed them prospectively for up to 30 months. The incidence of HIV-1 infection per 100 person-years among the initially seronegative partners was examined in relation to behavioral and biologic variables. Results The male partner was HIV-1–positive in 228 couples, and the female partner was HIV-1–positive in 187 couples. Ninety of the 415 initially HIV-1–negative partners seroconverted (incidence, 11.8 per 100 person-years). The rate of male-to-female transmission was not significantly different from the rate of female-to-male transmission (12.0 per 100 person-years vs. 11.6 per 100 person-years). The incidence of seroconversion was highest among ...
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TL;DR: A theoretical strategy of universal voluntary HIV testing and immediate treatment with ART, combined with present prevention approaches, could have a major effect on severe generalised HIV/AIDS epidemics.
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