Injecting 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

Increasing availability of illicit drugs among people who inject drugs in Bangkok, Thailand

BackgroundIn recent years, the Thai government has strengthened drug law enforcement as a strategy to address a continuing epidemic of illicit drug use. We sought to assess temporal trends in street-level availability of illicit drugs among injection drug users (IDUs) in Bangkok, Thailand. MethodsUsing univariate statistics and multivariate logistic regression, we assessed changes in the availability of five substances (heroin, methamphetamine, crystal methamphetamine, midazolam, and illicit methadone) between 2009 and 2011 and examined social, structural and individual factors influencing availability among community-recruited samples of IDUs in Bangkok. Availability was measured in three levels: immediate (available in ≤10min); moderate (available in 10–90min); and delayed (available in >90min; our reference category). ResultsThe analyses included 718 IDUs, including 165 (23.0%) women. Controlling for changes in participant characteristics between assessments, and in a period of constant nominal illicit drug prices, moderate availability of all substances increased significantly between 2009 and 2011, with adjusted odds ratios ranging between 2.36 (illicit methadone) and 4.61 (crystal methamphetamine) (all p<0.01). Immediate availability of all substances but heroin also increased (all p<0.01). More immediate availability of methamphetamine was also associated with a history of incarceration (p<0.05). ConclusionsDespite the Thai government's intensified drug suppression efforts, the availability of illicit drugs among IDUs in Bangkok increased significantly between 2009 and 2011. The findings raise concern about the overreliance on drug law enforcement-based approaches and point to the need for greater investment in evidence-based drug policies.

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.

Drug use and the risk of HIV infection amongst injection drug users participating in an HIV vaccine trial in Bangkok, 1999–2003

Background HIV spread rapidly amongst injecting drug users (IDUs) in Bangkok in the late 1980s. In recent years, changes in the drugs injected by IDUs have been observed. We examined data from an HIV vaccine trial conducted amongst IDUs in Bangkok during 1999–2003 to describe drug injection practices, drugs injected, and determine if drug use choices altered the risk of incident HIV infection. Methods The AIDSVAX B/E HIV vaccine trial was a randomized, double-blind, placebo-controlled trial. At enrolment and every 6 months thereafter, HIV status and risk behaviour were assessed. A proportional hazards model was used to evaluate demographic characteristics, incarceration, drug injection practices, sexual activity, and drugs injected during follow-up as independent predictors of HIV infection. Results The proportion of participants injecting drugs, sharing needles, and injecting daily declined from baseline to month 36. Amongst participants who injected, the proportion injecting heroin declined (98.6–91.9%), whilst the proportions injecting methamphetamine (16.2–19.6%) and midazolam (9.9–31.9%) increased. HIV incidence was highest amongst participants injecting methamphetamine, 7.1 (95% CI, 5.4–9.2) per 100 person years. Injecting heroin and injecting methamphetamine were independently associated with incident HIV infection. Conclusions Amongst AIDSVAX B/E vaccine trial participants who injected drugs during follow-up, the proportion injecting heroin declined whilst the proportion injecting methamphetamine, midazolam, or combinations of these drugs increased. Controlling for heroin use and other risk factors, participants injecting methamphetamine were more likely to become HIV-infected than participants not injecting methamphetamine. Additional HIV prevention tools are urgently needed including tools that address methamphetamine use.

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.

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.

HIV Type 1 Incidence Estimates by Detection of Recent Infection from a Cross-Sectional Sampling of Injection Drug Users in Bangkok: Use of the IgG Capture BED Enzyme Immunoassay

Development of serologic tests to detect recent HIV-1 infection has generated worldwide interest in applying this approach to estimate incidence. We previously devised an IgG-capture BED-EIA (or BED-CEIA) that detects increasing levels of anti-HIV IgG following seroconversion to identify recent infection and to estimate incidence among persons infected with diverse HIV-1 subtypes worldwide. Injection drug users (IDUs; n = 1969) were screened in 1996 for participation in a prospective cohort study. Serum specimens from 594 IDUs were HIV-1 seropositive (30.2%) and were tested with the BED-CEIA. The proportion of recent infections and estimated incidence by different epidemiological risk factors were compared with incidence data measured from the prospective cohort. Of 594 HIV-1-seropositive specimens, 113 (19%) were identified as recent infections. Overall, the estimated annual incidence among persons screened was 17.3%/year (95% CI, 12.8-24.2%/year) compared with 9.0%/year (95% CI, 6.7-11.9%/year) measured from the prospective cohort during the same time period. Estimated incidence was higher among younger aged and unemployed IDUs as well as among those who injected more frequently, confirming previously reported risk factors from this prospective cohort. As persons screened from a cross-sectional sampling probably have higher risk for HIV than selected uninfected individuals who choose to participate and receive risk reduction counseling in a longitudinal cohort study, use of this or other serologic testing strategies to identify populations with high incidence (such as for HIV vaccine trials) may overestimate incidence measured from prospective cohorts.

Genetic Analysis of Incident HIV-1 Strains Among Injection Drug Users in Bangkok: Evidence for Multiple Transmission Clusters During a Period of High Incidence

Genetic Analysis of Incident HIV-1 Strains Among Injection Drug Users in Bangkok: Evidence for Multiple Transmission Clusters During a Period of High Incidence

Higher Viral Loads and Other Risk Factors Associated With HIV-1 Seroconversion During a Period of High Incidence Among Injection Drug Users in Bangkok

Higher Viral Loads and Other Risk Factors Associated With HIV-1 Seroconversion During a Period of High Incidence Among Injection Drug Users in Bangkok

Genetic analysis of incident HIV-1 strains among injection drug users in Bangkok: evidence for multiple transmission clusters during a period of high incidence.

During 1995-1996, 1,209 HIV-1-negative injection drug users (IDUs) attending methadone treatment clinics operated by the Bangkok Metropolitan Administration in Bangkok, Thailand, were enrolled in a prospective cohort study. Through 1998, 133 of these IDUs had seroconverted to HIV-1; 130 of these seroconverters were included in this study. HIV-1 CRF01_AE and subtype B strains accounted for 79% and 21% of the incident infections, respectively. To examine phylogenetic relationships among these incident HIV-1 strains, we used several phylogenetic inference methodologies to analyze the env (C2-V4) sequences in blood samples collected soon after seroconversion. These analyses consistently revealed eight phylogenetic clusters comprising 21 incident strains (bootstrap method, >80%; six CRF01_AE and two subtype B clusters). Two factors were found to be associated with the eight clusters. The first factor was temporal: seven of the eight clusters comprised 17 sequences from IDUs whose estimated dates of seroconversion were within a period of high incidence from July 1996 through January 1997. The second factor was a possible geographic association: four clusters were observed among IDUs who had attended the same methadone treatment clinics. These phylogenetic clusters likely represent subgroups within larger HIV transmission networks among IDUs in Bangkok. Despite prevention efforts, the incidence of HIV-1 infection among the Bangkok IDU population continues to be high. A better understanding of transmission networks and factors associated with such networks can help guide prevention efforts.

Higher viral loads and other risk factors associated with HIV-1 seroconversion during a period of high incidence among injection drug users in Bangkok.

We analyzed data from a prospective cohort study of injection drug users (IDUs) attending methadone treatment clinics in Bangkok, Thailand, during 1995-1998 to characterize factors associated with a period of high incidence (PHI) from July 1996 through January 1997 compared with periods of lower incidence. Sociobehavioral characteristics were similar for all participants during and outside the PHI except for the following: there was more reported drug injection while IDUs were incarcerated during the PHI (odds ratio, 1.67; p =.02) and significantly higher proportions of persons reported heroin injection (91% vs. 75%, respectively; p =.02) and higher frequencies of daily injection and sharing of injection equipment (40% vs. 25%, respectively; p =.05) during the PHI than outside the PHI. Through most of the first year after seroconversion, plasma HIV-1 loads were significantly higher in persons who seroconverted during the PHI than in those who seroconverted outside the PHI. Higher viral loads may potentially contribute to faster disease progression and increased infectiousness or transmissibility to subsequent contacts. Our findings suggest that prevention efforts to reduce the effective size and turnover within IDU sharing networks may have a significant impact on the epidemic by disrupting the rapid transmission of HIV-1 from recently infected, highly infectious individuals.

The impact of a partially effective HIV vaccine on a population of intravenous drug users in Bangkok, Thailand: a dynamic model.

Because of the variability of HIV, the first AIDS vaccine is likely to be only partially effective. There is some concern among scientists that a low-efficacy vaccine could worsen the HIV epidemic if vaccinated individuals increase their risk behavior under the false assumption of immunity. To address this concern, we constructed a dynamic compartmental model that simulated the course of the HIV/AIDS epidemic in a population of injection drug users in Bangkok, Thailand. The model calculated long-term HIV prevalence, number of AIDS cases, and total population size for two scenarios: vaccination program versus no vaccination program. We used sensitivity analyses to evaluate the impact of postvaccination risk behavior change on HIV prevalence. A 75% effective vaccine led to a 40-year HIV prevalence of 37% with vaccination and 50% without vaccination. Postvaccination behavior change had only a limited effect on the results with a 75% effective vaccine but a significant effect with a 30% effective vaccine. If 90% of low-risk individuals responded to a 30% effective vaccine with increased high-risk behavior, the benefit of vaccination disappeared. These results agree with analyses of the epidemic among gay men. If injection drug behavior is indeed modifiable, our findings have significant policy and planning implications.