***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background The HPTN 052 trial confirmed that antiretroviral therapy ( ART ) can nearly eliminate HIV transmission from successfully treated HIV-infected individuals within couples . Here , we present the mathematical modeling used to inform the design and monitoring of a new trial aim ing to test whether widespread provision of ART is feasible and can substantially reduce population -level HIV incidence . Methods and Findings The HPTN 071 ( PopART ) trial is a three-arm cluster-r and omized trial of 21 large population clusters in Zambia and South Africa , starting in 2013 . A combination prevention package including home-based voluntary testing and counseling , and ART for HIV positive individuals , will be delivered in arms A and B , with ART offered universally in arm A and according to national guidelines in arm B. Arm C will be the control arm . The primary endpoint is the cumulative three-year HIV incidence . We developed a mathematical model of heterosexual HIV transmission , informed by recent data on HIV-1 natural history . We focused on realistically modeling the intervention package . Parameters were calibrated to data previously collected in these communities and national surveillance data . We predict that , if targets are reached , HIV incidence over three years will drop by > 60 % in arm A and > 25 % in arm B , relative to arm C. The considerable uncertainty in the predicted reduction in incidence justifies the need for a trial . The main drivers of this uncertainty are possible community-level behavioral changes associated with the intervention , uptake of testing and treatment , as well as ART retention and adherence . Conclusions The HPTN 071 ( PopART ) trial intervention could reduce HIV population -level incidence by > 60 % over three years . This intervention could serve as a paradigm for national or supra-national implementation . Our analysis highlights the role mathematical modeling can play in trial development and monitoring , and more widely in evaluating the impact of treatment as prevention This paper examines HIV risk behavior among HIV-uninfected adults living with people taking antiretroviral therapy ( ART ) in Ug and a. A prospect i ve cohort of 455 HIV-uninfected non-spousal household members of ART patients receiving home-based AIDS care was enrolled . Sexual behavior , HIV risk perceptions , AIDS-related anxiety , and the perception that AIDS is curable were assessed at baseline , 6 , 12 and 24 months . Generalized linear mixture models were used to model risk behavior over time and to identify behavioral correlates . Overall , risky sex decreased from 29 % at baseline to 15 % at 24-months . Among women , risky sex decreased from 31 % at baseline to 10 % at 6 months and 15 % at 24 months . Among men , risky sex decreased from 30 % at baseline to 8 % at 6 months and 13 % at 24 months . Perceiving HIV/AIDS as curable and lower AIDS-related anxiety were independently associated with risky sex . No evidence of behavioral disinhibition was observed . Concerns regarding behavioral disinhibition should not slow down efforts to increase ART access in Africa BACKGROUND R and omised trials show that male circumcision reduces the prevalence and incidence of high-risk human papillomavirus ( HPV ) infection in men . We assessed the efficacy of male circumcision to reduce prevalence and incidence of high-risk HPV in female partners of circumcised men . METHODS In two parallel but independent r and omised controlled trials of male circumcision , we enrolled HIV-negative men and their female partners between 2003 and 2006 , in Rakai , Ug and a. With a computer-generated r and om number sequence in blocks of 20 , men were assigned to undergo circumcision immediately ( intervention ) or after 24 months ( control ) . HIV-uninfected female partners ( 648 of men from the intervention group , and 597 of men in the control group ) were simultaneously enrolled and provided interview information and self-collected vaginal swabs at baseline , 12 months , and 24 months . Vaginal swabs were tested for high-risk HPV by Roche HPV Linear Array . Female HPV infection was a secondary endpoint of the trials , assessed as the prevalence of high-risk HPV infection 24 months after intervention and the incidence of new infections during the trial . Analysis was by intention-to-treat . An as-treated analysis was also done to account for study -group crossovers . The trials were registered , numbers NCT00425984 and NCT00124878 . FINDINGS During the trial , 18 men in the control group underwent circumcision elsewhere , and 31 in the intervention group did not undergo circumcision . At 24-month follow-up , data were available for 544 women in the intervention group and 488 in the control group ; 151 ( 27·8 % ) women in the intervention group and 189 ( 38·7 % ) in the control group had high-risk HPV infection ( prevalence risk ratio=0·72 , 95 % CI 0·60 - 0·85 , p=0·001 ) . During the trial , incidence of high-risk HPV infection in women was lower in the intervention group than in the control group ( 20·7 infections vs 26·9 infections per 100 person-years ; incidence rate ratio=0·77 , 0·63 - 0·93 , p=0·008 ) . INTERPRETATION Our findings indicate that male circumcision should now be accepted as an efficacious intervention for reducing the prevalence and incidence of HPV infections in female partners . However , protection is only partial ; the promotion of safe sex practice s is also important . FUNDING The Bill & Melinda Gates Foundation , National Institutes of Health , and Fogarty International Center BACKGROUND Preexposure prophylaxis with antiretroviral drugs has been effective in the prevention of  human immunodeficiency virus ( HIV ) infection  in some trials but not in others . METHODS In this r and omized , double-blind , placebo-controlled trial , we assigned 2120 HIV-negative women in Kenya , South Africa , and Tanzania to receive either a combination of tenofovir disoproxil fumarate and emtricitabine ( TDF-FTC ) or placebo once daily . The primary objective was to assess the effectiveness of TDF-FTC  in preventing HIV acquisition and to evaluate safety . RESULTS HIV infections occurred in 33 women in the TDF-FTC group ( incidence rate , 4.7 per 100 person-years ) and in 35 in the placebo group ( incidence rate , 5.0 per 100 person-years ) , for an estimated hazard ratio in the TDF-FTC group of 0.94 ( 95 % confidence interval , 0.59 to 1.52 ; P=0.81 ) . The proportions of women with nausea , vomiting , or elevated alanine aminotransferase levels were significantly higher in the TDF-FTC group ( P=0.04 , P<0.001 , and P=0.03 , respectively ) . Rates of drug discontinuation because of hepatic or renal abnormalities were higher in the TDF-FTC group ( 4.7 % ) than in the placebo group ( 3.0 % , P=0.051 ) . Less than 40 % of the HIV-uninfected women in the TDF-FTC group had evidence of recent pill use at visits that were matched to the HIV-infection window for women with seroconversion . The study was stopped early , on April 18 , 2011 , because of lack of efficacy . CONCLUSIONS Prophylaxis with TDF-FTC did not significantly reduce the rate of HIV infection and was associated with increased rates of side effects , as compared with placebo . Despite substantial counseling efforts , drug adherence appeared to be low . ( Supported by the U.S. Agency for International Development and others ; FEM-PrEP Clinical Trials.gov number , NCT00625404 . ) BACKGROUND Antiretroviral preexposure prophylaxis is a promising approach for preventing human immunodeficiency virus type 1 ( HIV-1 ) infection  in heterosexual population s. METHODS We conducted a r and omized trial of oral antiretroviral therapy for use as preexposure prophylaxis among HIV-1-serodiscordant heterosexual couples from Kenya and Ug and a. The HIV-1-seronegative partner in each couple was r and omly assigned to one of three study regimens -- once-daily tenofovir ( TDF ) , combination tenofovir-emtricitabine ( TDF-FTC ) , or matching placebo-- and followed monthly for up to 36 months . At enrollment , the HIV-1-seropositive partners were not eligible for antiretroviral therapy , according to national guidelines . All couples received st and ard HIV-1 treatment and prevention services . RESULTS We enrolled 4758 couples , of whom 4747 were followed : 1584 r and omly assigned to TDF , 1579 to TDF-FTC , and 1584 to placebo . For 62 % of the couples followed , the HIV-1-seronegative partner was male . Among HIV-1-seropositive participants , the median CD4 count was 495 cells per cubic millimeter ( interquartile range , 375 to 662 ) . A total of 82 HIV-1 infections occurred in seronegative participants during the study , 17 in the TDF group ( incidence , 0.65 per 100 person-years ) , 13 in the TDF-FTC group ( incidence , 0.50 per 100 person-years ) , and 52 in the placebo group ( incidence , 1.99 per 100 person-years ) , indicating a relative reduction of 67 % in the incidence of HIV-1 with TDF ( 95 % confidence interval [ CI ] , 44 to 81 ; P<0.001 ) and of 75 % with TDF-FTC ( 95 % CI , 55 to 87 ; P<0.001 ) . Protective effects of TDF-FTC and TDF alone against HIV-1 were not significantly different ( P=0.23 ) , and both study medications significantly reduced the HIV-1 incidence among both men and women . The rate of serious adverse events was similar across the study groups . Eight participants receiving active treatment were found to have been infected with HIV-1 at baseline , and among these eight , antiretroviral resistance developed in two during the study . CONCLUSIONS Oral TDF and TDF-FTC both protect against HIV-1 infection in heterosexual men and women . ( Funded by the Bill and Melinda Gates Foundation ; Partners PrEP Clinical Trials.gov number , NCT00557245 . ) Objectives : To evaluate the preparedness for phase 2/IIb/III microbicide trials at 4 clinical trial sites : Durban and Hlabisa ( South Africa ) , Lusaka ( Zambia ) , and Moshi ( Tanzania ) . Design : A prospect i ve cohort study was undertaken to assess site suitability for microbicide efficacy studies . Study objectives included assessing sites ' ability to recruit and retain high-risk women with the appropriate HIV incidence rates needed to conduct microbicide efficacy studies . Methods : Nine hundred fifty-eight consenting women were enrolled and followed for up to 1 year . Demographic , behavioral , laboratory , and clinical data were collected to determine the incidence rates of HIV , sexually transmitted infections , and pregnancy . Results : Accrual was completed in 6.3 , 6.7 , 7.1 , and 8.3 months in Durban , Hlabisa , Moshi , and Lusaka , respectively . The highest month 12 participant retention rate was recorded in Durban ( 97 % ) , followed by Hlabisa ( 94 % ) , Moshi ( 86 % ) , and Lusaka ( 93 % ) . Mean overall age of enrolled participants was 28.6 years ( ranging from 27.0 to 32.2 years ) across sites . Despite condom counseling , rates of condom use were slightly lower at study end . Pregnancy incidence in the study as a whole was 20.2 per 100 women-years ( wy ) . Overall HIV prevalence was 32.5 % , and overall HIV incidence was 3.8 per 100 wy ( 95 % confidence interval [ CI ] : 2.6 to 5.2 ) . HIV incidence per site was 5.3 per 100 wy in Durban ( 95 % CI : 2.7 to 9.2 ) , 6.2 per 100 wy in Hlabisa ( 95 % CI : 3.4 to 10.5 ) ; 2.6 per 100 wy in Lusaka ( 95 % CI : 1.0 to 5.8 ) , and 1.4 per 100 wy in Moshi ( 95 % CI : 0.3 to 4.0 ) . Conclusions : Preparatory studies provide accurate local estimates of HIV incidence , recruitment and retention rates , and behavioral characteristics of targeted population s for large-scale clinical trials . Determining these factors allows for better preparation for design , sample size , and appropriate population for future selection of trial sites . Because of the lower than expected HIV incidence observed at the Moshi site , only the South African and Zambian sites were selected for the phase 2/II 
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CONCLUSIONS With the exception of serodiscordant couples , there is variable evidence that awareness of one 's serostatus leads to substantial changes in risk behaviour among HIV-negative individuals .