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: The risk of HIV acquisition varied widely, and the estimates for receptive anal intercourse increased compared with previous estimates, while the risk associated with sexual intercourse was reduced most substantially by the combined use of condoms and antiretroviral treatment of HIV-infected partners.
Abstract: Background: Effective HIV prevention programs rely on accurate estimates of the peract risk of HIV acquisition from sexual and parenteral exposures. We updated the previous risk estimates of HIV acquisition from parenteral, vertical, and sexual exposures, and assessed the modifying effects of factors including condom use, male circumcision, and antiretroviral therapy. Methods: We conducted literature searches to identify new studies reporting data regarding per-act HIV transmission risk and modifying factors. Of the 7339 abstracts potentially related to per-act HIV transmission risk, three meta-analyses provided pooled per-act transmission risk probabilities and two studies provided data on modifying factors. Of the 8119 abstracts related to modifying factors, 15 relevant articles, including three meta-analyses, were included. We used fixed-effects inversevariance models on the logarithmic scale to obtain updated estimates of certain transmission risks using data from primary studies, and employed Poisson regression to calculate relative risks with exact 95% confidence intervals for certain modifying factors. Results: Risk of HIV transmission was greatest for blood transfusion, followed by vertical exposure, sexual exposures, and other parenteral exposures. Sexual exposure risks ranged from low for oral sex to 138 infections per 10000 exposures for receptive anal intercourse. Estimated risks of HIV acquisition from sexual exposure were attenuated by 99.2% with the dual use of condoms and antiretroviral treatment of the HIVinfected partner. Conclusion: The risk of HIV acquisition varied widely, and the estimates for receptive anal intercourse increased compared with previous estimates. The risk associated with sexualintercourse was reducedmostsubstantially bythe combineduse of condomsand antiretroviral treatment of HIV-infected partners. 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins AIDS 2014, 28:1509‐1519
635 citations
Cites background or methods from "HIV transmission risk through anal ..."
...A similar pooled estimate [140 per 10 000 exposures, 95% confidence interval (CI) 20–250] was calculated using a random-effects model [6]....
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...First, we established what was already known, starting with a series of recent systematic reviews and metaanalyses that were identified through a comprehensive literature review conducted for a related project that also examined per-act HIV transmission risk and provided estimates of pooled per-act HIV transmission probabilities for blood transfusion [5], parenteral exposures [5], receptive anal intercourse [6], receptive penile–vaginal intercourse [7], insertive penile–vaginal intercourse [7], and mother-to-child transmission [8]....
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...Summary of HIV transmission risk estimates The estimated per-act HIV transmission risk (all expressed as per 10 000 exposures) was greatest for blood transfusion [9250 (95% CI 8900–9610)], followed by mother-to-child transmission [2260 (95% CI 1700–2900)], receptive anal intercourse [138 (95% CI 102–186)], needle-sharing injection drug use [63 (95% CI 41–92)], and percutaneous needle stick injuries [23 (95% CI 0–46)] [5,6,8,10]....
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...A 2010 meta-analysis [6] provided an estimate of this risk based on data from...
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TL;DR: The results suggest that the risk of HIV transmission in gay couples through condomless sex when HIV viral load is suppressed is effectively zero, which supports the message of the U=U (undetectable equals untransmittable) campaign, and the benefits of early testing and treatment for HIV.
552 citations
TL;DR: In this paper, a multistep, static, deterministic model was used to estimate the rate and number of HIV transmissions attributable to persons at each of the following 5 HIV care continuum steps: HIV infected but undiagnosed, HIV diagnosed but not retained in medical care, retained in care but not prescribed antiretroviral therapy, prescribed antirrhoehrgical therapy but not virally suppressed, and virally suppressing.
Abstract: Importance Human immunodeficiency virus (HIV) transmission risk is primarily dependent on behavior (sexual and injection drug use) and HIV viral load. National goals emphasize maximizing coverage along the HIV care continuum, but the effect on HIV prevention is unknown. Objectives To estimate the rate and number of HIV transmissions attributable to persons at each of the following 5 HIV care continuum steps: HIV infected but undiagnosed, HIV diagnosed but not retained in medical care, retained in care but not prescribed antiretroviral therapy, prescribed antiretroviral therapy but not virally suppressed, and virally suppressed. Design, Setting, and Participants A multistep, static, deterministic model that combined population denominator data from the National HIV Surveillance System with detailed clinical and behavioral data from the National HIV Behavioral Surveillance System and the Medical Monitoring Project to estimate the rate and number of transmissions along the care continuum. This analysis was conducted January 2013 to June 2014. The findings reflect the HIV-infected population in the United States in 2009. Main Outcomes and Measures Estimated rate and number of HIV transmissions. Results Of the estimated 1 148 200 persons living with HIV in 2009, there were 207 600 (18.1%) who were undiagnosed, 519 414 (45.2%) were aware of their infection but not retained in care, 47 453 (4.1%) were retained in care but not prescribed ART, 82 809 (7.2%) were prescribed ART but not virally suppressed, and 290 924 (25.3%) were virally suppressed. Persons who are HIV infected but undiagnosed (18.1% of the total HIV-infected population) and persons who are HIV diagnosed but not retained in medical care (45.2% of the population) were responsible for 91.5% (30.2% and 61.3%, respectively) of the estimated 45 000 HIV transmissions in 2009. Compared with persons who are HIV infected but undiagnosed (6.6 transmissions per 100 person-years), persons who were HIV diagnosed and not retained in medical care were 19.0% (5.3 transmissions per 100 person-years) less likely to transmit HIV, and persons who were virally suppressed were 94.0% (0.4 transmissions per 100 person-years) less likely to transmit HIV. Men, those who acquired HIV via male-to-male sexual contact, and persons 35 to 44 years old were responsible for the most HIV transmissions by sex, HIV acquisition risk category, and age group, respectively. Conclusions and Relevance Sequential steps along the HIV care continuum were associated with reduced HIV transmission rates. Improvements in HIV diagnosis and retention in care, as well as reductions in sexual and drug use risk behavior, primarily for persons undiagnosed and not receiving antiretroviral therapy, would have a substantial effect on HIV transmission in the United States.
474 citations
TL;DR: The evidence and knowledge gaps that affect the HIV epidemic in TSW are summarized, a deterministic model based on findings related to HIV risks and interventions is developed, and a research agenda to improve HIV services and policies is proposed.
303 citations
TL;DR: Addressing the expanding epidemics of HIV in MSM will require continued research, increased resources, political will, policy change, structural reform, community engagement, and strategic planning and programming, but it can and must be done.
Abstract: Epidemics of HIV in MSM continue to expand in most low, middle, and upper income countries in 2013 and rates of new infection have been consistently high among young MSM. Current prevention and treatment strategies are insufficient for this next wave of HIV spread. We conducted a series of comprehensive reviews of HIV prevalence and incidence, risks for HIV, prevention and care, stigma and discrimination, and policy and advocacy options. The high per act transmission probability of receptive anal intercourse, sex role versatility among MSM, network level effects, and social and structural determinants play central roles in disproportionate disease burdens. HIV can be transmitted through large MSM networks at great speed. Molecular epidemiologic data show marked clustering of HIV in MSM networks, and high proportions of infections due to transmission from recent infections. Prevention strategies that lower biological risks, including those using antiretrovirals, offer promise for epidemic control, but are limited by structural factors including, discrimination, criminalization, and barriers to healthcare. Subepidemics, including among racial and ethnic minority MSM in the United States and UK, are particularly severe and will require culturally tailored efforts. For the promise of new and combined bio-behavioral interventions to be realized, clinically competent healthcare is necessary and community leadership, engagement, and empowerment are likely to be key. Addressing the expanding epidemics of HIV in MSM will require continued research, increased resources, political will, policy change, structural reform, community engagement, and strategic planning and programming, but it can and must be done.
289 citations
Cites background from "HIV transmission risk through anal ..."
...[44] have reported, is the very high transmission efficiency of receptive anal intercourse – at an estimated 1....
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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.
1,948 citations