***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 A large epidemic of HIV-1 subtype B began among injection drug users ( IDUs ) in Bangkok in 1988 . Despite ongoing prevention efforts , HIV-1 prevalence among IDUs remained at 30–50 % through the 1990s . Objectives To measure the incidence of HIV-1 infection and related risk factors to guide prevention efforts and to evaluate the feasibility of conducting an HIV vaccine efficacy trial . Design and methods A prospect i ve cohort study in which IDUs attending methadone treatment programs in Bangkok were screened during 1995–1996 for enrollment into the study . IDUs found to be HIV-seronegative on two occasions were offered enrollment with follow-up visits every 4 months . On each visit participants were evaluated with a  question naire and serologic testing .  Results A total of 1209 HIV-negative IDUs were enrolled . Through the end of 1998 , the overall HIV-1 incidence rate was 5.8 ( 95 % confidence interval , 4.8–6.8 ) per 100 person – years of follow-up . HIV-1 subtypes E and B accounted for 79 and 21 % of infections , respectively . On multivariate analysis , HIV-1 seroconversion was primarily associated with the frequency of heroin injection , the sharing of injection equipment , and incarceration , especially with drug injection . Sexual behavior was not associated with increased risk for HIV-1 . Risk factors for infection with HIV-1 subtypes E and B were similar . Conclusion HIV-1 transmission risk remains high among Bangkok IDUs despite methadone treatment and other current prevention strategies . There is an urgent need to address this ongoing epidemic , especially in jails and prisons . This study led to the initiation in 1999 of a phase III HIV-1 vaccine efficacy trial in this population Objective : A recent report suggesting declining HIV transmission rates in southern India has been based on HIV seroprevalence data to estimate HIV incidence . We analyzed HIV incidence rates among 3 cohorts ( male , female non-sex worker , female sex worker [ FSW ] ) presenting to sexually transmitted infection ( STI ) clinics in Pune , India over 10 years . Methods : Between 1993 and 2002 , consenting HIV-uninfected individuals were enrolled in a prospect i ve study of the risks for HIV seroconversion . St and ardized HIV incidence estimates were calculated separately for the 3 cohorts . Results : HIV acquisition risk declined by more than 70 % for FSWs ( P = 0.02 ) and men ( P < 0.001 ) attending the STI clinics . There was no significant reduction in HIV incidence among women attending STI clinics ( P = 0.74 ) . The decline in HIV acquisition risk among male patients with STIs was associated with an increase in reported condom use with recent FSW contact and a decrease in genital ulcer disease . Conclusions : We report the first direct evidence for a decline in HIV incidence rates in FSWs and male patients with STIs over time . The lack of change in HIV infection risk among non-sex worker women highlights the need for additional targeted HIV prevention interventions BACKGROUND In Thail and , phase 1/2 trials of monovalent subtype B and bivalent subtype B/E ( CRF01_AE ) recombinant glycoprotein 120 human immunodeficiency virus type 1 ( HIV-1 ) vaccines were successfully conducted from 1995 to 1998 , prompting the first HIV-1 vaccine efficacy trial in Asia . METHODS This r and omized , double-blind , placebo-controlled efficacy trial of AIDSVAX B/E ( VaxGen ) , which included 36-months of follow-up , was conducted among injection drug users ( IDUs ) in Bangkok , Thail and . The primary end point was HIV-1 infection ; secondary end points included plasma HIV-1 load , CD4 cell count , onset of acquired immunodeficiency syndrome-defining conditions , and initiation of antiretroviral therapy . RESULTS A total of 2546 IDUs were enrolled between March 1999 and August 2000 ; the median age was 26 years , and 93.4 % were men . The overall HIV-1 incidence was 3.4 infections/100 person-years ( 95 % confidence interval [ CI ] , 3.0 - 3.9 infections/100 person-years ) , and the cumulative incidence was 8.4 % . There were no differences between the vaccine and placebo arms . HIV-1 subtype E ( 83 vaccine and 81 placebo recipients ) accounted for 77 % of infections . Vaccine efficacy was estimated at 0.1 % ( 95 % CI , -30.8 % to 23.8 % ; P=.99 , log-rank test ) . No statistically significant effects of the vaccine on secondary end points were observed . CONCLUSION Despite the successful completion of this efficacy trial , the vaccine did not prevent HIV-1 infection or delay HIV-1 disease progression The study objective was to assess willingness of men who have sex with men ( MSM ) enrollled in a vaccine preparedness study ( ' Projeto Rio ' ) to participate in phase III anti-HIV/AIDS vaccine trials . Overall , 57 % of Projeto Rio participants stated they would participate in a putative vaccine trial . MSM who reported commercial sex work were significantly ( p<0.05 ) more likely to engage in risky behaviours than others . In bivariate analysis , commercial sex workers ( CSWs ) were significantly ( p<0.05 ) more likely than non-commercial sex workers ( NCSWs ) to be willing to participate in vaccine trials ( 62.6 % versus 51.4 % ) . Among those willing , CSWs reported significantly more often ( p<0.05 ) ( 50.5 % ) than NCSWs ( 38.0 % ) that they would enroll to protect themselves from HIV . In multivariate analyses , variables associated with willingness to participate ( WTP ) were lower educational level , positive serology for syphilis , and ' engagement , under the influence of alcohol , in risky sexual practice s that would normally be avoided ' , but not commercial sex work . The potential enrollment in vaccine trials of MSM CWSs , as well as participants of low socio-economic status and high risk , seems thus to be possible Summary : In preparation for HIV vaccine trials , data on a cohort 's knowledge about vaccines and vaccine studies are required so as to tailor educational material s to adequately meet local needs . Interviews ( n = 1,182 ) conducted as part of a 3‐year prospect i ve study of Ug and an military men aged 18 to 30 years determined what information , in addition to st and ard trials information , would be required to ensure comprehension of trial procedures . The interviews highlighted four points : ( 1 ) the cohort has a lot of knowledge about vaccines but conflates whether vaccines cure or prevent disease ; ( 2 ) there is a general lack of knowledge about clinical trials procedures ; ( 3 ) the desire to be protected from HIV/AIDS is a common reason for being willing to participate in a hypothetical vaccine trial ; and ( 4 ) concern about side effects is a common reason for being unwilling to participate in a trial . These four points guided the focus of the vaccine trials education , which used locally appropriate analogies to introduce complex unfamiliar concepts such as placebos and blinding . This case study highlights the value of incorporating baseline interviews to assess the educational needs of study population Objectives : To describe recruitment , screening and baseline characteristics of injection drug users ( IDU ) participating in a phase III HIV vaccine ( AIDSVAX ® B/E ; VaxGen , USA ) trial and to compare enrollment characteristics between trial participants and 1209 IDU from a 1995–1998 vaccine trial preparatory cohort for changes that might impact trial design assumptions . Methods : Enrollment for both studies was conducted at Bangkok narcotic treatment clinics , where a st and ardized question naire was administered on demographics , risk behavior and incarceration history over the previous 6 months . Results : During 1999–2000 , 4943 IDU were screened for enrollment ; successful sources of recruitment included clinic attendees ( 43.4 % ) , an IDU referral program ( 20.4 % ) and preparatory cohort participants ( 14.7 % ) . Of those screened , 1689 ( 34 % ) were HIV seropositive ( HIV subtype B 23.6 % ; subtype E 76.4 % ) . Of the 2545 enrolled , 93.4 % were male . Compared with cohort IDU , trial IDU were younger ( mean age : 28.8 versus 31.3 years ) , better educated ( secondary level or higher : 67.2 % versus 58.7 % ) , and less likely to inject drugs daily ( 39.4 % versus 90.4 % ) ; they were more likely to have been incarcerated ( 78.4 % versus 65.7 % ) , have recently injected stimulants ( 14.8 % versus 5.8 % ) and tranquilizers ( 11.5 % versus 2.3 % ) , and obtained needles/syringes from a source other than a pharmacist ( 7.2 % versus 3.9 % ) ( all P ⩽ 0.003 ) . Conclusions : IDU at high risk for HIV have been successfully enrolled in the AIDSVAX ® B/E efficacy trial . Only minor epidemiologic differences were found at enrollment between trial and preparatory cohort IDU . The latter has proven critical in guiding trial design ; results are expected in late 2003 We assessed willingness to participate in an HIV recombinant gp120 bivalent subtypes B/E c and i date vaccine efficacy trial among 193 injection drug users ( IDUs ) attending drug treatment clinics in Bangkok , Thail and . IDUs previously enrolled in a prospect i ve cohort study were invited to group sessions describing a potential trial , then completed question naires assessing comprehension and willingness to participate . A week later , they completed a follow-up question naire that again assessed comprehension and willingness to participate , as well as barriers to and positive motives for participation , with whom ( if anyone ) they talked about the information , and whether others thought participation was a good , bad , or neutral idea . At baseline , 51 % were definitely willing to participate , and at follow-up 54 % ; only 3 % were not willing to participate at either time . Comprehension was high at baseline and improved at follow-up . Participants who viewed altruism , regular HIV tests , and family support for participation as important were more willing to volunteer . Frequency of incarceration and concerns about the length of the trial , possible vaccine-induced accelerated disease progression , and lack of family support were negatively associated with willingness . Overall , IDUs comprehended the information needed to make a fully informed decision about participating in an rgp120 vaccine efficacy trial and expressed a high level of willingness to participate in such a trial From May through August 1995 , a cross-sectional survey was conducted among injecting drug users ( IDUs ) drawn from 15 drug treatment clinics in Bangkok and who were not known to be HIV-seropositive , to determine the prevalence of HIV-1 subtypes B and E and related risk behaviors , and to offer enrollment in a prospect i ve cohort study . IDUs who voluntarily consented were interviewed , and blood specimens were tested for the presence of HIV antibodies . HIV-1-seropositive specimens were tested for subtypes B ' ( Thai B ) and E by using V3 loop peptide enzyme immunoassays specific for these HIV-1 genetic subtypes . Of 1674 IDUs studied , the mean age was 31.2 years ( interquartile range , 25 - 37 years ) , 94.8 % were men , and 29.3 % were HIV-1-seropositive . On multiple logistic regression analysis , HIV-1 seropositivity was associated with older age , not being married , less education , needle sharing , and incarceration . HIV-1 subtype B ' accounted for 65 % of prevalent infections and subtype E , 35 % . Infection with subtype E was associated with younger age and did not seem to be associated with sexual risk behaviors , which were uncommon in general . Bangkok IDUs continue to be at high risk for HIV-1 infection related to needle sharing and incarceration . Although HIV-1 subtype B ' accounts for most prevalent infections , subtype E seems to be more prevalent among younger IDUs , and most infections seem likely to result from parenteral transmission Background : Results of most population ‐based studies primarily are derived from people who responded positively and thereby continued to participate in such studies . It is , however , equally important to know the characteristics of study subjects who drop out to learn the reasons that kept them from continuing to participate in the study , especially because they had initially agreed to participate in such a study . In studies with long‐term follow‐up , reasons for nonresponse may provide invaluable information that may be gathered through continued contact with study subjects who have withdrawn from the study . Objectives : To determine characteristics of study participants who withdrew from an ongoing study of police officers , which involved counseling and HIV testing , and to determine reasons for their discontinued participation . Methods : Demographic characteristics of a cohort of police officers who had been participating in a study to determine their suitability for HIV vaccine trials were analyzed . Characteristics of those who did not return for the second survey of appointments for HIV testing were compared with those who continued their participation . A r and omly 
    Output:
    
In general , retention rates and WTP have been adequate to conduct HIV vaccine trials .
Educational programs to improve knowledge about HIV vaccines may contribute to better follow-up and an increased WTP in these countries