***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: Objectives : To evaluate the effect of hormonal contraception including combined oral contraceptives ( COCs ) , and the injectable progestins depo-medroxyprogesterone acetate ( DMPA ) and norethisterone enanthate ( Net-En ) on the  risk of HIV acquisition among women in South Africa . Design / methods : We analyzed data from 5567 women aged 16–49 years participating in the Carraguard Phase 3 Efficacy Trial . Participants were interviewed about contraceptive use and sexual behaviors and underwent pelvic examinations and HIV testing quarterly . We used marginal structural Cox regression models to estimate the effect of hormonal contraception exposure on HIV acquisition risk among women overall and among young women ( 16–24 years ) in particular . Results : Two hundred and seventy participants became HIV-infected ( 3.7 per 100 woman-years ) ; HIV incidence was 2.8 , 4.6 , 3.5 and 3.4 per 100 woman-years in the COC , DMPA , Net-En and nonhormonal contraceptive groups , respectively ( P = 0.09 ) . The adjusted hazard ratios ( AHRs ) were 0.84 [ 95 % confidence interval ( CI ) 0.51–1.39 ] , 1.28 ( 95 % CI 0.92–1.78 ) and 0.92 ( 95 % CI 0.64–1.32 ) among COC , DMPA and Net-En users , respectively , compared with the nonhormonal group controlling for covariates . Age modified the effect of hormonal contraception on HIV acquisition risk ; among young women , the AHRs were 1.02 ( 95 % CI 0.46–2.28 ) for COCs , 1.68 ( 95 % CI 0.96–2.94 ) for DMPA and 1.36 ( 95 % CI0.78–2.35 ) for Net-En users . Conclusions : In this study conducted among South African women , hormonal contraception did not significantly increase the risk of HIV acquisition . However , the effect estimate does not rule out a moderate increase in HIV risk associated with DMPA use found in some other recent studies BACKGROUND Hormonal contraceptives are used widely but their effects on HIV-1 risk are unclear . We aim ed to assess the association between hormonal contraceptive use and risk of HIV-1 acquisition  by women and HIV-1 transmission from HIV-1-infected women to their male partners . METHODS In this prospect i ve study , we followed up 3790 heterosexual HIV-1-serodiscordant couples participating in two longitudinal studies of HIV-1 incidence in seven African countries . Among  injectable and oral hormonal contraceptive users and non-users , we compared rates of HIV-1 acquisition by women and HIV-1 transmission from women to men . The primary outcome measure was HIV-1 seroconversion . We used Cox proportional hazards regression and marginal structural modelling to assess the effect of contraceptive use on HIV-1 risk . FINDINGS Among 1314 couples in which the HIV-1-seronegative partner was female ( median follow-up 18·0 [ IQR 12·6 - 24·2 ] months ) , rates of HIV-1 acquisition were 6·61 per 100 person-years in women who used hormonal contraception and 3·78 per 100 person-years in those who did not ( adjusted hazard ratio 1·98 , 95 % CI 1·06 - 3·68 , p=0·03 ) . Among 2476 couples in which the HIV-1-seronegative partner was male ( median follow-up 18·7 [ IQR 12·8 - 24·2 ] months ) , rates of HIV-1 transmission from women to men were 2·61 per 100 person-years in couples in which women used hormonal contraception and 1·51 per 100 person-years in couples in which women did not use hormonal contraception ( adjusted hazard ratio 1·97 , 95 % CI 1·12 - 3·45 , p=0·02 ) . Marginal structural model analyses generated much the same results to the Cox proportional hazards regression . INTERPRETATION Women should be counselled about potentially increased risk of HIV-1 acquisition and transmission  with hormonal contraception , especially injectable methods , and about the importance of dual protection with condoms to decrease HIV-1 risk  . Non-hormonal or low-dose hormonal contraceptive methods should be considered for women with or at-risk for HIV-1 . FUNDING US National Institutes of Health and the Bill & Melinda Gates Foundation Policymakers and public health research ers have dem and ed better evidence of the effects of interventions on public health and health inequalities and have pointed to the relative absence of rigorous outcome evaluations in this area . While most of these commentators agree that health inequalities are a problem , the means of tackling them often seems to rest on poor evidential foundations . This is no longer surprising , as the problem has been well-documented and the solution probably seems clear : if there is not enough evidence , then obviously we need more ; and if the evidence is ‘ weak ’ , well , then , it just needs to be ‘ stronger ’ in future . The funding environment in the UK , at least , is supportive of the production of this new , stronger evidence , with several new funding initiatives which are aim ing to foster the production of new evaluations of public health interventions . However , it might be useful to consider further what ‘ more evidence ’ might look like ( that is , what sort of evidence is needed ) and how might it be ‘ stronger ’ than in the past and also to consider what additional challenges collecting this new evidence might bring . It is clear that evidence on the effectiveness and cost-effectiveness of public health interventions is often missing . Sometimes this is because policies are insufficiently subjected to outcome evaluation , perhaps because it is assumed that they are mostly beneficial and any positive outcomes can be taken as read . R and omized controlled trials of policies are particularly uncommon and there are a variety of real and perceived barriers to trials . This means that the public are frequently ‘ enrolled ’ in real-life policy ‘ experiments ’ without giving their explicit consent , or indeed without any real prospect of anyone learning anything substantial about the effects of those interventions . Although the experimental nature of most policies is generally unacknowledged , this is not always the The use of hormonal contraception has been associated with an increased risk of HIV-1  in some studies but not in others . We analysed data from a 10-year prospect i ve cohort study of female sex workers in Mombasa , Kenya . In multivariate analysis , women using the injectable contraceptive depot medroxyprogesterone acetate and women using oral contraceptive pills were at increased risk of HIV-1 acquisition compared with women using no contraceptive method Objective : To evaluate the effect of oral and injectable hormonal contraception on the  risk of HIV acquisition among women in South Africa and Zimbabwe . Design : Secondary data analysis of 4913 sexually active women aged 18–49 years followed for up to 24 months in the Methods for Improving Reproductive Health in Africa ( MIRA ) phase III effectiveness trial of the diaphragm and lubricant gel  for HIV prevention . Methods : Participants were interviewed quarterly about contraception and sexual behavior and were tested for pregnancy , HIV , and other sexually transmitted infections . We used a Cox proportional hazards marginal structural model , weighted by the inverse probability of hormonal contraception use , to compare the risk of HIV acquisition among nonpregnant women reporting use of combined oral contraceptive pills ( COC ) , progestin-only pills ( POP ) , and /or injectable hormonal contraception to women not using these methods . Results : During the study , 283 participants seroconverted . Use of oral contraceptives ( POP or COC ) was not associated with HIV risk [ adjusted hazard ratio ( HRa ) = 0.86 , 95 % confidence interval ( CI ) 0.32 , 1.78 ] . Injectable hormonal contraception was associated with a small nonsignificant risk of HIV infection ( HRa = 1.34 , 95 % CI 0.75 , 2.37 ) . The effect of injectable hormonal contraception was similar in the unweighted site-adjusted only ( HRa = 1.32 , 95 % CI 1.00 , 1.74 ) and baseline factor adjusted models ( HRa = 1.27 , 95 % CI 0.94 , 1.72 ) . Conclusions : In this study , oral contraceptives were not associated with HIV acquisition . There is substantial uncertainty in the effect of injectable hormonal contraception on HIV risk . These findings underscore the importance of dual protection with condoms and the need for diverse contraceptive options for women at risk of HIV infection The aim of this study was to determine HIV-1 incidence among women of reproductive age in Malawi . A prospect i ve study design was followed . HIV-1 uninfected women were followed up for nine visits during a period of 12 months . At baseline , women received HIV-1 counselling and testing . At each visit , venous blood was collected for HIV-1 testing .  Incidence rate for HIV-1 was estimated using person-years of follow up ( PYFU ) . Risk factors for HIV acquisition were assessed using Cox proportional hazard models . A total of 842 HIV-1 negative women were enrolled in the study . Of these , 787 had subsequent HIV testing and 31 were found HIV-1 infected ; an overall incidence rate of 4.51 ( 95 % confidence interval : 2.96–6.06 ) per 100 PYFU was obtained . Young age , using hormonal injectable contraceptives and bacterial vaginosis were the main predictors of HIV acquisition . The incidence of HIV continues to be high among women in Malawi , and young women appear to be at higher risk Objectives : A r and omized , double-blind , placebo-controlled trial ( RCT ) of herpes simplex virus type 2 suppressive therapy with acyclovir 400 mg twice daily conducted among women in northwestern Tanzania reported a similar rate of HIV acquisition in both trial arms ( Current Controlled Trials number IS RCT N35385041 ) . Risk factors for HIV incidence were examined in the context of 3-monthly follow-up visits offering both voluntary counselling and testing and care for sexually transmitted infections . Design : Prospect i ve cohort analysis of trial participants enrolled and followed for up to 30 months . Methods : Risk factors for HIV acquisition were analysed using Cox regression . Results : Overall , 821 herpes simplex virus type 2 seropositive , HIV seronegative women were r and omized ; 400 r and omized to acyclovir and 421 to placebo ; 659 ( 80.3 % ) completed follow-up . HIV incidence was 4.27 per 100 person-years . There was no overall impact of acyclovir on HIV incidence [ hazard ratio = 1.01 ; 95 % confidence interval ( CI ) 0.61–1.66 ] . HIV acquisition was independently associated with younger age at enrolment ( age 16–19 vs. 30–35 : hazard ratio = 4.02 ; 95 % CI 1.67–9.68 ) , alcohol consumption at enrolment ( ≥30 drinks/week vs. none : hazard ratio = 4.39 , 95 % CI 1.70–11.33 ) , having paid sex within the previous 3 months ( hazard ratio = 1.82 , 95 % CI 1.09–3.05 ) , recent infection with gonorrhoea ( hazard ratio = 3.62 , 95 % CI 1.62–8.08 ) and injections in the previous 3 months ( hazard ratio = 3.45 , 95 % CI 1.62–7.34 ) . There was some evidence of an association between HIV incidence and living in the recruitment community for less than 2 years ( hazard ratio = 1.75 , 95 % CI 0.98–3.10 ) and exposure to hormonal contraception ( hazard ratio = 1.60 , 95 % CI 0.93–2.76 ) . Conclusion : A high incidence of HIV was observed in this trial cohort , especially in young women . Interventions are needed to address the risk associated with alcohol use and to sustain control of other sexually transmitted infections OBJECTIVES The heterosexual spread of HIV-1 is occurring at different rates in different parts of the world . The transmission probability of HIV-1 per sexual contact is low , but may be greatly enhanced by several cofactors . Sexually transmitted diseases ( STD ) , especially genital ulcers , may be such factors . So far , epidemiological evidence that other STD facilitate HIV-1 transmission is weak . The objective of this study was to determine whether treatable STD enhanced sexual transmission of HIV-1 in a cohort of female prostitutes in Kinshasa , Zaire . METHODS We conducted a nested case-control study of 431 initially HIV-1-negative women followed prospect ively for a mean duration of 2 years ( with monthly STD check-ups and 3-monthly HIV-1 serology )  . Cases ( seroconverters , n = 68 ) were compared with controls ( women who remained HIV-1-negative , n = 126 ) for incidence of STD and sexual exposure during the presumed period of HIV-1 ac 
    Output:
    
INTERPRETATION Our findings show a moderate increased risk of HIV acquisition for all women using depot medroxyprogesterone acetate , with a smaller increase in risk for women in the general population .