***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: Objective To determine the effects of a behavioural intervention for prevention of HIV and sexually transmitted diseases that identified , trained , and engaged leaders of Roma ( Gypsy ) men 's social networks to counsel their own network members . Design A two arm r and omised controlled trial . Setting A disadvantaged , impoverished Roma settlement in Bulgaria . Participants 286 Roma men from 52 social networks recruited in the community . Intervention At baseline all participants were assessed for HIV risk behaviour , tested and treated for sexually transmitted diseases , counselled in risk reduction , and r and omised to intervention or control groups . Network leaders learnt how to counsel their social network members on risk prevention . Networks were followed up three and 12 months after the intervention to determine evidence of risk reduction . Main outcome measure Occurrence of unprotected intercourse during the three months before each assessment . Results Reported prevalence of unprotected intercourse in the intervention group fell more than in control group ( from 81 % and 80 % , respectively , at baseline to 65 % and 75 % at three months and 71 % and 86 % at 12 months ) . Changes were more pronounced among men with casual partners . Effects remained strong at long term follow-up , consistent with changes in risk reduction norms in the social network . Other measures of risk reduction corroborated the intervention 's effects . Conclusions Endorsement and advice on HIV prevention from the leader of a social network produces well maintained change in the reported sexual practice s in members of that network . This model has particular relevance for health interventions in population s such as Roma who may be distrustful of outsiders . Trial registration Clinical Trials NCT00310973 OBJECTIVE Social norms have been associated with a wide range of health behaviors . In this study , the authors examined whether the social norms of HIV risk behaviors are clustered within social networks and whether the norms of network members are linked to the risk behaviors of their social network members . DESIGN Data were collected from the baseline assessment of 354 networks with 933 participants in a network-oriented HIV prevention intervention targeting injection drug users in Philadelphia , United States , and Chiang Mai , Thail and . MAIN OUTCOME MEASURES Four descriptive HIV risk norms of sharing needles , cookers , and cotton and front- or back-loading among friends who inject were assessed . RESULTS Three of 4 injection risk norms ( sharing needle , cookers , and cotton ) were found to be significantly clustered . In Philadelphia , 1 network member 's ( the index participant ) norms of sharing needles and front- or back-loading were found to be significantly associated with the network members ' risk behaviors , and the norm of sharing cotton was marginally associated . CONCLUSION The results of this study suggest that among injection drug users , social norms are clustered within networks ; social networks are a meaningful level of analyses for underst and ing how social norms lead to risk behaviors , providing important data for intervening to reduce injection-related HIV risks BACKGROUND Effective interventions are needed to prevent acquisition of HIV infection in men who have sex with men . To date , no behavioural interventions specifically for this risk group have been tested with HIV infection as the primary outcome . METHODS This multisite two-group r and omised controlled phase IIb trial tested the efficacy of a behavioural intervention in preventing HIV infection among 4295 men who have sex with men . The experimental intervention consisted of ten one-on-one counselling sessions followed by maintenance sessions every 3 months . The st and ard condition was twice-yearly Project RESPECT individual counselling . Twice-yearly follow-up visits included testing for HIV antibody and assessment of behavioural outcomes . FINDINGS The rate of acquisition of HIV infection was 18.2 % ( 95 % CI -4.7 to 36.0 ) lower in the intervention group than the st and ard group . Adjustment for baseline covariates attenuated the intervention effect to 15.7 % ( -8.4 to 34.4 ) . The effect was more favourable in the first 12 - 18 months of follow-up . The occurrence of unprotected receptive anal intercourse with HIV-positive and unknown-status partners was 20.5 % ( 10.9 to 29.0 ) lower in the intervention than in the st and ard group . INTERPRETATION The results from the primary analyses allow us to rule out that the experimental intervention is associated with a 35 % lower rate of HIV acquisition than in the st and ard group . The overall estimate of a difference of 18.2 % , more favourable estimates of effect in the first 12 - 18 months , and similar effects on risk behaviours suggest that prevention of HIV infection among men who have sex with men by a behavioural intervention is feasible . Further work should be done to develop more effective interventions Objective : To evaluate the effects of an HIV prevention intervention with social networks of young men who have sex with men ( YMSM ) in St. Petersburg , Russia and Sofia , Bulgaria . Design : A two-arm r and omized trial with a longitudinally-followed community cohort . Methods : Fifty-two MSM social networks were recruited through access points in high-risk community venues . Network members ( n = 276 ) were assessed to determine risk characteristics , administered sociometric measures to empirically identify the social leader of each network , and counseled in risk reduction . The leaders of 25 experimental condition networks attended a nine-session program that provided training and guidance in delivering ongoing theory-based HIV prevention advice to other network members . Leaders successively targeted network members ’ AIDS risk-related knowledge and risk reduction norms , attitudes , intentions , and self-efficacy . Participants were re-administered risk assessment measures at 3- and 12-month follow-ups . Results : Among changes produced , the percentage of experimental network members reporting unprotected intercourse ( UI ) declined from 71.8 to 48.4 % at 3-month follow up ( P = 0.0001 ) . The percentage who engaged in UI with multiple partners reduced from 31.5 to 12.9 % ( P = 0.02 ) . After 12 months , the effects became attenuated but remained among participants who had multiple recent sexual partners , the most vulnerable group . Little change was found in control group networks . Conclusions : Interventions that engage the identified influence leaders of at-risk YMSM social networks to communicate theory-based counseling and advice can produce significant sexual risk behavior change . This model is culturally pertinent for HIV prevention efforts in former socialist countries , as well as elsewhere for other hard-to-reach vulnerable community population Despite numerous behavioral interventions design ed for women , rates of HIV and STIs are increasing . Interventions are needed that reach a large number of at-risk individuals . This study was a r and omized clinical trial of a HIV/STI behavioral intervention conducted in Baltimore , MD , USA . Heterosexual women ( n = 169 ) completed a baseline and three semiannual follow-up visits . Participants were r and omized into a st and ard of care comparison condition or a Peer Mentor condition . At the 6-month follow-up , Peer Mentors were less likely to have multiple sex partners [ AOR : 0.28 ( 95 % CI : 0.13 , 0.63 ) ] . At the 18 month follow-up assessment , Peer Mentors increased their condom use during vaginal [ AOR : 0.47 ( 95 % CI : 0.25 , 0.87 ) ] and anal sex [ AOR : 0.24 ( 95 % CI : 0.09 , 0.68 ) ] as well as with main [ AOR : 0.41 ( 95 % CI : 0.21 , 0.77 ) ] and non-main partners [ AOR : 0.33 ( 95 % CI : 0.14 , 0.79 ) ] . Peer education is a sustainable approach to change risky sexual behaviors . ResumenA pesar de numerosas intervenciones de comportamientos diseñadas para las mujeres , están aument and o las tasas de VIH y enfermedades de transmisión sexual . Se necesitan intervenciones que llegar a un gran número de personas en situación de riesgo . Este estudio fue un ensayo clínico aleatorio de un VIH/ITS intervención conductual llevó a cabo en Baltimore , MD , USA . Las mujeres heterosexuales ( n = 169 ) completó una línea de base y 3 visitas de seguimiento semestral . Los participantes fueron asignados al azar en un estándar de afección de comparación de atención o un Mentor del mismo nivel . En el seguimiento de 6 meses , mentores de Peer tenían menos probabilidades de tener múltiples compañeros sexuales [ AOR : 0,28 ( 95 % CI : 0,13 , 0.63 ) ] . En la evaluación de seguimiento de 18 meses , mentores de Peer aumentó su uso de condón durante vaginal [ AOR : 0,47 ( 95 % CI : 0,25 , 0.87 ) ] y sexo anal [ AOR : 0,24 ( 95 % CI : 0,09 , 0,68 ) ] , así como con el principal [ AOR : 0,41 ( 95 % CI : 0,21 , 0,77 ) ] y no principales asociados [ AOR : 0,33 ( 95 % CI : 0,14 ; 0.79 ) ] . La educación entre compañeros es un enfoque sostenible para cambiar los comportamientos sexuales riesgosos HIV prevention , by intervening within social networks , is potentially important but highly understudied . Approaches that systematic ally identify , train , and enlist known social influence leaders to advise members of their own networks in risk reduction constitute ways to reach hidden population segments , persons who are distrustful of authorities but trust their peers , and those who can not be reached through traditional professionally delivered counseling . This article illustrates and provides evaluation data on a program that recruited 14 intact social networks of young men who have sex with men ( YMSM ) in St. Petersburg , Russia , and Sofia , Bulgaria . Sociometric measures were used to identify the social leader of each network , and baseline  risk assessment measures were administered to all members of each social network . The sociometrically determined leaders then attended a six-session group program that provided training and guidance in how to carry out theory-based and tailored HIV prevention conversations with members of their own social networks . Four months after leaders completed the program , all network members were readministered risk assessment measures . Pre- to postintervention data revealed that the program produced : ( 1 ) increases in the level and comfort with which network members talked about AIDS prevention topics in their daily conversations ; ( 2 ) increased network-level AIDS risk reduction knowledge and improved risk reduction norm perceptions , attitudes , behavioral intentions , and self-efficacy ; and ( 3 ) increased condom use levels among network members . Although not a controlled , r and omized trial , these program evaluation findings strongly support the feasibility of social network-level HIV prevention approaches AIMS To assess the effectiveness of a peer-based , personal risk network-focused HIV prevention intervention to ( i ) train injection drug users ( IDUs ) to reduce injection and sex risk behaviors , ( ii ) conduct outreach to behaviorally risky individuals in their personal social networks [ called risk network members ( RNM ) ] , and ( iii ) reduce RNM HIV risk behaviors . DESIGN R and omized controlled trial with prospect i ve data collection at 6 , 12 and 18 months . Intervention condition consisted of five group sessions , one individual session and one session with Index and the RNM . SETTING This study was conducted in Baltimore , Maryl and from March 2004 to March 2006 . PARTICIPANTS ( i ) Index participants were aged ≥ 18 years and self-reported injection drug use in the prior 6 months and ( ii ) their RNM who were aged ≥ 18 years and drug users or sex partners of Index . MEASUREMENTS Outcomes included : ( i ) injection risk based on sharing needles , cookers and cotton for injection and drug splitting , ( ii ) sex risk based on number of sex partners , condom use and exchanging sex and ( iii ) Index HIV outreach behaviors . FINDINGS A total of 227 Index participants recruited 336 RNM . Retention of Index at 18-month follow-up exceeded 85 % . Findings suggest that the experimental condition was efficacious at 18 months in reducing Index participant injection risk [ odds ratio ( OR ) = 0.38 ; 95 % confidence interval ( CI ) = 0.18 - 0.77 ) , drug-splitting risk ( OR = 0.46 ; 95 % CI = 0.25 - 0.88 ) and sex risk among Index ( OR = 0.53 ; 95 % CI = 0.34 - 0.86 ) . Significant intervention effect on increased condom use among female RNM was observed ( OR = 0.34 ; 95 % CI = 0.18 - 0.62 ) . CONCLUSIONS Training active IDU to promote HIV prevention with behaviorally risky individuals in their networks is feasible , efficacious and sustainable Since the 1990s , there has been a proliferation of methamphetamine use in Thail and , particularly among young people . Simultaneously , risky sexual behaviors among this population have increased . This study examined the effects of a peer network intervention and a life-skills intervention on methamphetamine and HIV risk behaviors  among 18 - 25 year olds in Chiang Mai , Thail and . Between April 2005 and June 2007 , we conducted a r and omized behavioral trial to compare the efficacy of a peer educator , network-oriented intervention with a best practice , life-skills curriculum on  methamphetamine use , sexual behaviors , and incident sexually transmitted infections ( STIs ) . Follow- 
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There were large differences in how social network members were identified and involved in the interventions .
This systematic review highlights the potential utility of social network-based condom promotion programs .
Se necesita más investigación para demostrar cómo estas estudias promovedoras pueden desarrollar