Drug Users In Bangkok Research Articles

Mexican perspective on the Mosaico HIV vaccine trial

Disappointment among researchers and the community is inevitable following the decision to interrupt the Mosaico phase 3 HIV vaccine trial 1 HVTNPhase 3 Mosaic-based investigational HIV vaccine study discontinued following disappointing results of planned data review. https://www.hvtn.org/news/news-releases/2023/01/phase-3-mosaic-based-investigational-hiv-vaccine-study-discontinued-following-disappointing-results-planned-data-review.htmlDate: 2023 Date accessed: January 25, 2023 Google Scholar on the basis of the preplanned data and safety monitoring board analysis in January, 2023. After more than four decades of efforts to develop a vaccine to protect against HIV, Mosaico was the eighth clinical trial to reach an advanced stage in vaccine development (phase 2b/3). Failure to show efficacy is very frustrating after many years of sustained and committed work. 2 Flynn NM Forthal DN Harro CD Judson FN Mayer KH Para MF Placebo-controlled phase 3 trial of a recombinant glycoprotein 120 vaccine to prevent HIV-1 infection. J Infect Dis. 2005; 191: 654-665 Crossref PubMed Scopus (775) Google Scholar , 3 Pitisuttithum P Gilbert P Gurwith M et al. Randomized, double-blind, placebo-controlled efficacy trial of a bivalent recombinant glycoprotein 120 HIV-1 vaccine among injection drug users in Bangkok, Thailand. J Infect Dis. 2006; 194: 1661-1671 Crossref PubMed Scopus (680) Google Scholar , 4 Buchbinder SP Mehrotra DV Duerr A et al. Efficacy assessment of a cell-mediated immunity HIV-1 vaccine (the Step Study): a double-blind, randomised, placebo-controlled, test-of-concept trial. Lancet. 2008; 372: 1881-1893 Summary Full Text Full Text PDF PubMed Scopus (1407) Google Scholar , 5 Hammer SM Sobieszczyk ME Janes H et al. Efficacy trial of a DNA/rAd5 HIV-1 preventive vaccine. N Engl J Med. 2013; 369: 2083-2092 Crossref PubMed Scopus (455) Google Scholar , 6 Gray GE Bekker L-G Laher F et al. Vaccine efficacy of ALVAC-HIV and bivalent subtype C gp120-MF59 in adults. N Engl J Med. 2021; 384: 1089-1100 Crossref PubMed Scopus (79) Google Scholar

Pre-exposure Prophylaxis Uptake, Adherence, and Persistence: A Narrative Review of Interventions in the U.S.

Since 2012, HIV pre-exposure prophylaxis (PrEP) has been available to prevent HIV transmission; yet, uptake, adherence, and persistence to PrEP have been suboptimal. This narrative review examines the latest interventions and programs to improve all 3 stages of PrEP adherence and reviews ongoing studies to promote effective PrEP use. From 2017 to 2020, a total of 20 studies analyzed different individual- and structural-level approaches to increase PrEP adherence, including behavior change interventions, technology-based interventions (e.g., short message service messages and mobile applications), and alternate delivery strategies (e.g., pharmacy-based PrEP, integration with other services, and home delivery). Most published interventions involved men who have sex with men, although 3 assessed women (2 transgender, 1 cisgender). Randomized, controlled data support 3 behavioral change interventions and 1 technology-based intervention. Alternate delivery strategies seem promising, although more robust study designs are generally needed. In addition, data on the alignment of ongoing HIV risk and PrEP persistence (i.e., prevention-effective adherence) were limited. The authors also identified 20 ongoing studies that are promoting PrEP adherence. Future work should be inclusive of all at-risk groups in the U.S., including African American and Latinx heterosexual populations and people who inject drugs. Proven and promising approaches may work well in combination and may also need to be adapted with the introduction of long-acting pre-exposure prophylaxis formulations. Collectively, this body of work indicates considerable progress toward understanding the role PrEP adherence will play in Ending the HIV Epidemic in the U.S. that will be bolstered by the outcomes of ongoing trials.

Prophylactic tenofovir reduced HIV infection in injectable drug users

Source Citation Choopanya K, Martin M, Suntharasamai P, et al; Bangkok Tenofovir Study Group. Antiretroviral prophylaxis for HIV infection in injecting drug users in Bangkok, Thailand (the Bangkok Tenofovir Study): a randomised, double-blind, placebo-controlled phase 3 trial. Lancet. 2013;381:2083-90. 23769234

Antiretroviral prophylaxis for HIV infection in injecting drug users in Bangkok, Thailand (the Bangkok Tenofovir Study): a randomised, double-blind, placebo-controlled phase 3 trial

Antiretroviral pre-exposure prophylaxis reduces sexual transmission of HIV. We assessed whether daily oral use of tenofovir disoproxil fumarate (tenofovir), an antiretroviral, can reduce HIV transmission in injecting drug users. In this randomised, double-blind, placebo-controlled trial, we enrolled volunteers from 17 drug-treatment clinics in Bangkok, Thailand. Participants were eligible if they were aged 20-60 years, were HIV-negative, and reported injecting drugs during the previous year. We randomly assigned participants (1:1; blocks of four) to either tenofovir or placebo using a computer-generated randomisation sequence. Participants chose either daily directly observed treatment or monthly visits and could switch at monthly visits. Participants received monthly HIV testing and individualised risk-reduction and adherence counselling, blood safety assessments every 3 months, and were offered condoms and methadone treatment. The primary efficacy endpoint was HIV infection, analysed by modified intention-to-treat analysis. This trial is registered with ClinicalTrials.gov, number NCT00119106. Between June 9, 2005, and July 22, 2010, we enrolled 2413 participants, assigning 1204 to tenofovir and 1209 to placebo. Two participants had HIV at enrolment and 50 became infected during follow-up: 17 in the tenofovir group (an incidence of 0·35 per 100 person-years) and 33 in the placebo group (0·68 per 100 person-years), indicating a 48·9% reduction in HIV incidence (95% CI 9·6-72·2; p=0·01). The occurrence of serious adverse events was much the same between the two groups (p=0·35). Nausea was more common in participants in the tenofovir group than in the placebo group (p=0·002). In this study, daily oral tenofovir reduced the risk of HIV infection in people who inject drugs. Pre-exposure prophylaxis with tenofovir can now be considered for use as part of an HIV prevention package for people who inject drugs. US Centers for Disease Control and Prevention and the Bangkok Metropolitan Administration.

High rates of midazolam injection and associated harms in Bangkok, Thailand

To identify the prevalence and correlates of midazolam injection among injecting drug users in Thailand. Serial cross-sectional mixed-methods study. Bangkok, Thailand. A total of 435 adults who had injected drug(s) in the past 6 months were recruited through peer outreach and word of mouth in Bangkok in 2011. Multivariable logistic regression was used to analyze self-reported data collected through an interviewer-administered survey in July-October 2011 (n = 435). Additionally, qualitative data were collected in June-July 2009 (n = 10) and analyzed to explore the health problems attributable to midazolam injection. Among 435 survey participants, the prevalence of daily midazolam injection in the past 6 months was 37.0% (95% confidence interval: 32-42). While 75.8% of the daily midazolam injectors identified heroin as their drug of choice, 91.8% of these individuals reported substituting heroin with midazolam when heroin was unavailable. In multivariable analyses, daily midazolam injection was associated with femoral vein injection [adjusted odds ratio (AOR) = 4.48], polydrug use (AOR = 4.94), daily heroin injection (AOR = 3.25), binge use (AOR = 1.75) and perceived increase in policing pressure (AOR = 1.95) (all P < 0.05). Qualitative accounts indicated severe health problems associated with midazolam injection, including nerve and vascular injuries. Midazolam misuse is increasing among injecting drug users in Bangkok and appears to be used primarily as a substitute for heroin. Midazolam injection was associated independently with various risk factors for injection-related complications. Given the many deleterious effects of midazolam injection, novel interventions for midazolam injectors are needed urgently.

Collective Empowerment While Creating Knowledge: A Description of a Community-Based Participatory Research Project With Drug Users in Bangkok, Thailand

In light of growing concerns regarding the ongoing drug war in Thailand and a lack of support for people who inject drugs in this setting, in 2008, we undertook a community-based participatory research project involving a community of active drug users at a peer-run drop-in center in Bangkok. This case study describes a unique research partnership developed between academic and active drug users and demonstrates that participatory approaches can help empower this vulnerable population while generating valid research. Further research is needed to explore ways of optimizing community-based participatory research methods when applied to drug-using populations.

Factors associated with methadone treatment among injection drug users in Bangkok, Thailand

Little is known about the characteristics of injection drug users (IDU) who take methadone treatment in Thailand. We examined prevalence and correlates of methadone treatment among a community-recruited sample of IDU in Bangkok, Thailand. Among 273 participants, 143 (52.4%) reported accessing methadone treatment within the previous 6 months. Older age (adjusted odds ratio [AOR] = 1.90, 95% confidence interval [CI] = 1.10–3.30) and more than weekly midazolam injection (AOR = 1.85, 95% CI = 1.04–3.29) were positively associated, whereas alcohol use (AOR = 0.34, 95% CI = 0.18–0.63) and noninjection methamphetamine use (AOR = 0.49, 95% CI = 0.29–0.85) were negatively associated with methadone treatment. In subanalyses, 98.6% of IDU on methadone continued to inject drugs, and the most common reason for stopping methadone was becoming incarcerated (49%). Evidence-based addiction treatment in the form of methadone maintenance therapy, with attention paid to concomitant midazolam injection in this setting, should be implemented.

Compulsory drug detention center experiences among a community-based sample of injection drug users in Bangkok, Thailand

BackgroundDespite Thailand's official reclassification of drug users as "patients" deserving care and not "criminals," the Thai government has continued to rely heavily on punitive responses to drug use such as "boot camp"-style compulsory "treatment" centers. There is very little research on experiences with compulsory treatment centers among people who use drugs. The work reported here is a first step toward filling that gap.MethodsWe examined experiences of compulsory drug treatment among 252 Thai people who inject drugs (IDU) participating in the Mitsampan Community Research Project in Bangkok. Multivariate logistic regression was used to identify factors independently associated with a history of compulsory treatment experience.ResultsIn total, 80 (31.7%) participants reported a history of compulsory treatment. In multivariate analyses, compulsory drug detention experience was positively associated with current spending on drugs per day (adjusted odds ratio [AOR] = 1.86; 95%CI: 1.07 - 3.22) and reporting drug planting by police (AOR = 1.81; 95%CI: 1.04 - 3.15). Among those with compulsory treatment experience, 77 (96.3%) reported injecting in the past week, and no difference in intensity of drug use was observed between those with and without a history of compulsory detention.ConclusionThese findings raise concerns about the current approach to compulsory drug detention in Thailand. Exposure to compulsory drug detention was associated with police abuse and high rates of relapse into drug use, although additional research is needed to determine the precise impact of exposure to this form of detention on future drug use. More broadly, compulsory "treatment" based on a penal approach is not consistent with scientific evidence on addressing drug addiction and should be phased out in favor of evidence-based interventions.

Low Uptake of Hepatitis C Testing and High Prevalence of Risk Behavior Among HIV-Positive Injection Drug Users in Bangkok, Thailand

Low Uptake of Hepatitis C Testing and High Prevalence of Risk Behavior Among HIV-Positive Injection Drug Users in Bangkok, Thailand

Methamphetamine injection and syringe sharing among a community-recruited sample of injection drug users in Bangkok, Thailand

The recent growth in methamphetamine use internationally has raised concerns about the relationship between methamphetamine use and HIV infection. However, the risks associated with methamphetamine injection have not been fully described, particularly outside of Western countries. Therefore, we sought to examine the relationship between methamphetamine injection and syringe sharing among injection drug users (IDU) in Bangkok, Thailand. Using bivariate statistics and multivariate logistic regression, we examined the prevalence of methamphetamine injection and the relationship between more than weekly methamphetamine injection and syringe sharing among a community-recruited sample of IDU participating in the Mitsampan Community Research Project in Bangkok. During June and July 2009, 311 IDU participated in this study, including 91 (29.3%) women. In total, 114 (36.7%) participants reported having injected methamphetamine ("yaba") twice or more per week in the past six months. In multivariate analyses, after adjustment for potential social, demographic and behavioral confounders, syringe sharing remained independently associated with injecting methamphetamine more than once per week (adjusted odds ratio=2.86, 95% confidence interval: 1.59-5.15). Over one-third of a community-recruited sample of Thai IDU reported more than weekly injection of methamphetamine, and methamphetamine injection was independently associated with syringe sharing. Essential HIV prevention services targeting IDU, such as syringe exchange and evidence-based addiction treatment, should be included in interventional efforts to address methamphetamine use in Thailand.

Overdose experiences among injection drug users in Bangkok, Thailand

BackgroundAlthough previous studies have identified high levels of drug-related harm in Thailand, little is known about illicit drug overdose experiences among Thai drug users. We sought to investigate non-fatal overdose experiences and responses to overdose among a community-recruited sample of injection drug users (IDU) in Bangkok, Thailand.MethodsData for these analyses came from IDU participating in the Mit Sampan Community Research Project. The primary outcome of interest was a self-reported history of non-fatal overdose. We calculated the prevalence of past overdose and estimated its relationship with individual, drug-using, social, and structural factors using multivariate logistic regression. We also assessed the prevalence of ever witnessing an overdose and patterns of response to overdose.ResultsThese analyses included 252 individuals; their median age was 36.5 years (IQR: 29.0 - 44.0) and 66 (26.2%) were female. A history of non-fatal overdose was reported by 75 (29.8%) participants. In a multivariate model, reporting a history of overdose was independently associated with a history of incarceration (Adjusted Odds Ratio [AOR] = 3.83, 95% Confidence Interval [CI]: 1.52 - 9.65, p = 0.004) and reporting use of drugs in combination (AOR = 2.48, 95% CI: 1.16 - 5.33, p = 0.019). A majority (67.9%) reported a history of witnessing an overdose; most reported responding to the most recent overdose using first aid (79.5%).ConclusionsExperiencing and witnessing an overdose were common in this sample of Thai IDU. These findings support the need for increased provision of evidence-based responses to overdose including peer-based overdose interventions.

Difficulty accessing syringes and syringe borrowing among injection drug users in Bangkok, Thailand

Thailand's longstanding HIV epidemic among injection drug users (IDU) has been attributed, in part, to the Thai government's unwillingness to implement evidence-based HIV prevention interventions. This study was undertaken to examine risk factors for syringe borrowing among a community-recruited sample of Thai IDU. We examined the prevalence of syringe borrowing among 238 IDU participating in the Mit Sampan Community Research Project, Bangkok. Multivariate logistic regression was used to identify independent predictors of syringe borrowing in the past 6 months. A total of 238 IDU participated in this study; 66 (26.2%) were female, and the median age was 36.5 years. In total, 72 (30.3%) participants reported borrowing a used syringe in the past 6 months, with 47 (65.3%) of these individuals reporting multiple borrowing events. In multivariate analyses, syringe borrowing was positively associated with difficulty accessing syringes [adjusted odds ratio (AOR) = 2.46; 95% confidence interval (CI): 1.08-5.60] and injecting with other people on a frequent basis (AOR = 3.17; 95% CI: 1.73-5.83). Primary reasons offered for experiencing difficulty accessing syringes included being too far from syringe outlets (34.1%), pharmacies being closed (13.6%) and being refused syringes at pharmacies (9.1%). We observed an alarmingly high rate of syringe borrowing among a community-recruited sample of Thai IDU. Various lines of evidence indicate that poor access to sterile syringes is driving the high rate of syringe borrowing observed in this study. Immediate action should be taken to increase access to sterile syringes among Thai IDU.

High rates of midazolam injection among drug users in Bangkok, Thailand

BackgroundReports from Thailand suggest that a growing number of people who inject drugs (IDU) are now injecting midazolam, a legal benzodiazepine with potent amnestic and ventilatory depressant effects. We therefore sought to examine midazolam injection among a community-recruited sample of Thai IDU.MethodsWe examined the prevalence and correlates of midazolam injection among 252 IDU participating in the Mitsampan Community Research Project, Bangkok, using multivariate logistic regression. We also examined the use of midazolam in combination with other drugs.Results252 IDU participated in this study, including 66 (26.2%) women. In total, 170 (67.5%) participants reported ever having injected midazolam, and 144 (57.1%) reported daily midazolam injection in the past six months. In multivariate analyses, a history of midazolam injection was independently associated with using drugs in combination (adjusted odds ratio [AOR] = 5.86; 95% confidence interval [CI]: 2.96-11.60), younger age (AOR = 0.43; 95%CI: 0.22-0.83), having a history of methadone treatment (AOR = 3.12, 95%CI: 1.55-6.90), and binge drug use (AOR = 2.25, 95%CI: 1.09-4.63). The drugs most commonly used in combination with midazolam were heroin (72.3%) and yaba (methamphetamine) (30.5%).ConclusionWe observed a high rate of midazolam injection among Thai IDU. Midazolam injection was strongly associated with polysubstance use and binge drug use, and was most commonly used in combination with both opiates and methamphetamines. Our findings suggest that midazolam injection has become increasingly common within Thailand. Evidence-based approaches for reducing harms associated with midazolam injection are needed.

Incarceration experiences among a community-recruited sample of injection drug users in Bangkok, Thailand

BackgroundSince 2003 Thailand has waged an aggressive "war on drugs" campaign focused on arresting and incarcerating suspected drug users and dealers. However, little is known about incarceration experiences among IDU in the wake of the recent war on drugs. Therefore, we sought to examine incarceration experiences among IDU in Bangkok, Thailand.MethodsWe examined the prevalence of incarceration among community-recruited IDU participating in the Mitsampan Community Research Project. Multivariate logistic regression was used to identify factors associated with a self-reported history of incarceration. We also examined the prevalence of injection drug use and syringe sharing within prisons.Results252 IDU were recruited in August 2008; 66 (26.2%) were female and the median age was 36.5 years. In total, 197 (78.2%) participants reported a history of incarceration. In multivariate analyses, reporting a history of incarceration was associated with a history of compulsory drug treatment (adjusted odds ratio [AOR] = 4.93; 95% confidence interval [CI]: 1.95 - 12.48), non-fatal overdose (AOR = 3.69; 95%CI: 1.45 - 9.39), syringe sharing (AOR = 2.20; 95%CI: 1.12 - 4.32), and female gender (AOR = 0.41; 95%CI: 0.20 - 0.82). Among those who reported a history of incarceration, 59 (29.9%) reported injection drug use in prison, and 48 (81.4%) of these individuals reported sharing syringes in prison. Incarceration was not associated with the number of injections performed in the previous week (p = 0.202).ConclusionOver three-quarters of the IDU participating in this study reported a history of incarceration, and 30% of these individuals reported injection drug use within prison. Further, an alarmingly high level of syringe sharing within prison was reported, and incarceration was not associated with reductions in drug use. These findings provide further evidence of the need for community diversion strategies, as well as harm reduction programs, in Thai prisons.

Reports of evidence planting by police among a community-based sample of injection drug users in Bangkok, Thailand

BackgroundDrug policy in Thailand has relied heavily on law enforcement-based approaches. Qualitative reports indicate that police in Thailand have resorted to planting drugs on suspected drug users to extort money or provide grounds for arrest. The present study sought to describe the prevalence and factors associated with this form of evidence planting by police among injection drug users (IDU) in Bangkok.MethodsMultivariate logistic regression was used to identify factors associated with evidence planting of drugs by police among a community-based sample of IDU in Bangkok. We also examined the prevalence and average amount of money paid by IDU to police in order to avoid arrest.Results252 IDU were recruited between July and August, 2008, among whom 66 (26.2%) were female and the median age was 36.5 years. In total, 122 (48.4%) participants reported having drugs planted on them by police. In multivariate analyses, this form of evidence planting was positively associated with midazolam use (Adjusted Odds Ratio [AOR] = 2.84; 95% Confidence Interval [CI]: 1.58 - 5.11), recent non-fatal overdose (AOR = 2.56; 95%CI: 1.40 - 4.66), syringe lending (AOR = 2.08; 95%CI: 1.19 - 3.66), and forced drug treatment (AOR = 1.88; 95%CI: 1.05 - 3.36). Among those who reported having drugs planted on them, 59 (48.3%) paid police a bribe in order to avoid arrest.ConclusionA high proportion of community-recruited IDU participating in this study reported having drugs planted on them by police. Drug planting was found to be associated with numerous risk factors including syringe sharing and participation in government-run drug treatment programs. Immediate action should be taken to address this form of abuse of power reportedly used by police.

Prevalence of hepatitis B, tetanus, hepatitis A, human immunodeficiency virus and feasibility of vaccine delivery among injecting drug users in Bangkok, Thailand, 2003–2005

To estimate the prevalence of hepatitis B virus (HBV), tetanus, hepatitis A virus (HAV) and human immunodeficiency virus (HIV) in injecting drug users (IDUs), risk factors associated with infection and the feasibility of HBV vaccine delivery in HBV seronegatives. Cross-sectional seroprevalence survey of 1535 IDUs recruited from 17 Bangkok Metropolitan Administration (BMA) methadone clinics and HBV vaccination of seronegatives. Prevalence of antibody to HBV, tetanus, HAV and HIV was 87.8%, 68.1%, 60.2% and 35.9%, respectively. Prevalence of HBV and HAV increased with increasing age; prevalence of tetanus decreased with increasing age. Being HIV seropositive was related inversely to income and being tetanus seronegative. Of the 189 HBV seronegative IDUs, 81.0% completed the vaccine series. IDUs with HIV had a 6.5-fold odds of vaccine non-response. These data underscore the need for, and feasibility of, vaccine delivery in this population and support targeting efforts at high-risk age groups.

The Spread of HIV-1 Subtypes B and CRF01_AE Among Injecting Drug Users in Bangkok, Thailand

The HIV epidemic among injecting drug users (IDUs) in Bangkok was initially dominated by HIV subtype B and later by the recombinant CRF01_AE. The present study investigates the distribution of the 2 variants in time and how it is affected by changes in injecting risk behavior and treatment. A mathematic model describing the spread of HIV subtype B and CRF01_AE among IDUs was developed, and data from the AIDSVAX B/E cohort of IDUs in Bangkok were used. From the model, it was calculated that during 1999 to 2003, the annual incidence of HIV was around 0.6 and 2.7 to 3.9 infections per 100 person-years for subtype B and CRF01_AE, respectively. Of the new infections, 18% and 72% are first infections with subtype B and CRF01_AE, respectively, and 9% are superinfections. With increases in risk behavior, the fraction of superinfections rises. If treatment reduces the infectivity of CRF01_AE more than that of subtype B, the fraction of subtype B infections should increase. Subtype B should remain prevalent in a small but considerable fraction of the population for a long time. Changes in risk behavior and the introduction of treatment may alter the distribution of subtypes, but CRF01_AE should remain dominant.

Respondent-driven sampling to assess characteristics and estimate the number of injection drug users in Bangkok, Thailand

Background Since early in Thailand's HIV epidemic, HIV seroprevalence among injection drug users (IDUs) in Bangkok has been around 40%. As Thailand moves to strengthen HIV prevention and care programs for Bangkok IDUs, information on current patterns of drug use and an estimate of the size and composition of the IDU population are essential. Methods We used respondent-driven sampling (RDS) to recruit Bangkok IDUs who reported injecting in the past 6 months. IDUs were interviewed with a standardized questionnaire. Logistic regression was used to compare IDUs currently or previously in treatment with those never treated. RDS software was used to estimate IDU population size based on the proportion in treatment. Results Of 963 IDUs recruited, 828 (86%) were men. One hundred and twelve IDUs (12%) reported never having attended a drug treatment clinic. Young age, unemployment, injection of single drug, and never having been HIV tested were significantly associated with never-in-treatment status. The estimated proportion of IDUs in treatment was 0.55 (95% confidence interval, 0.52–0.60). Dividing the known number of IDUs in treatment (1981 IDUs attending Bangkok drug treatment clinics during October 2003 through March 2004) by this proportion, we estimated the number of IDUs in Bangkok during the period of RDS to be 3595 (95% confidence interval, 3296–3810). Conclusions Data obtained through RDS, although subject to limitations from co-existing government drug control policies and possible under-recruitment of out-of-treatment IDUs, will be useful in informing policy, strengthening prevention approaches, and improving methods to monitor the HIV epidemic among Thai IDUs.

Randomized, Double‐Blind, Placebo‐Controlled Efficacy Trial of a Bivalent Recombinant Glycoprotein 120 HIV‐1 Vaccine among Injection Drug Users in Bangkok, Thailand

In Thailand, 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. This randomized, 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, Thailand. 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. 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. Despite the successful completion of this efficacy trial, the vaccine did not prevent HIV-1 infection or delay HIV-1 disease progression.

Estimating the number of drug users in Bangkok 2001: A capture–recapture approach using repeated entries in one list

Conventionally, capture-recapture techniques involving different lists such as police or hospitals are used for quantifying populations which are difficult to count, such as illicit drug user populations. Here, a novel approach is suggested based upon repeated entries in one list, which is less dependent on matching entries from different sources as in the conventional approach. For this purpose, a population-based study was conducted that utilizes all data on treatment episodes of drug users from all 61 health treatment centers in the Bangkok metropolitan region to estimate the size of drug use in the Bangkok metropolitan region. The data stem from the drug treatment surveillance system of the Office of the Narcotics Control Board (ONCB) and cover the period from October 1 to December 31, 2001. Based upon the frequency of treatment episodes of each patient, a count distribution arose which could be modelled well by means of a Poisson mixture model. Using this count model, an estimate for the number of unobserved drug users could be constructed. From 11,222 drug users found during the period, 7063 (62.9%) were heroin users, 3346 (29.8%) metamphetamine users, and the remaining 813 (7.3%) distributed under 15 drug categories, none above 1%. The study concentrated on heroin and metamphetamine users who were predominantly male (96.2% for heroin and 91.8% for metamphetamine). Metamphetamine users were younger than heroin users (22.3 years 95% CI: 22.1-22.5 vs. 30.8 years 95% CI: 30.6-31.0). By using the truncated Poisson mixture model, an estimate of the unobserved frequency of drug users with zero treatment episodes could be constructed leading to an estimate of 11,296 (95% CI: 8,964-13,628) heroin users (completeness of identification: 38.42, 95% CI: 34.03-44.04%) and 32,105 (95% CI: 24,647-39,563) metamphetamine users (completeness of identification: 9.44, 95% CI: 7.79-11.97%) for the Bangkok metropolitan region. The proposed model showed excellent goodness-of-fit, unspecified for drug type and also if specified for the major drug types which allowed the prediction of the unobserved number of drug users in a realistic way, avoiding artefacts due to severe matching problems when using several, different sources. The technique is also easy to implement and can be used routinely to monitor drug user populations in space and time.