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Preventing HIV Transmission: The Role of Sterile Needles and Bleach 7 The Effects of Needle Exchange Programs This chapter assesses the effects of needle exchange programs on HIV infections and drug use behaviors. Five major sources provide the evidentiary basis for the panel's assessment: (1) a 1991 review carried out by congressional request of the effectiveness of needle exchange programs (U.S. General Accounting Office, 1993), (2) a second comprehensive evaluation carried out by University of California researchers for the Centers for Disease Control and Prevention (Lurie et al., 1993), (3) selected studies published since the two 1993 literature reviews, (4) detailed examination of a set of recent studies in New Haven, Connecticut, and (5) detailed examination of a set of recent studies in Tacoma, Washington. This chapter concludes with the panel's conclusions and recommendations, which are based on the evidence presented in the chapter and throughout the report. Evaluations of needle exchange programs have been published by Stimson et al. (1988), Des Jarlais (1985), the U.S. General Accounting Office (GAO) (1993), and the University of California (Lurie et al., 1993). We highlight the findings of the latter two reports, which were commissioned specifically by the federal government as evaluations of needle exchange programs. Both were published in 1993 and deal with needle exchange programs as they existed up to that time. Needle exchange programs operate in a rapidly changing environment, and the panel reviews a number of studies that were published subsequent to the major reviews by GAO and the University of California. Two strong lines of evidence emerged from the panel's examination of recent research on the effects of needle exchange programs on the spread of
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach HIV infection: studies from New Haven and Tacoma. These two sets of studies were selected on the basis of the wealth of published information available about the programs they analyze. That is, not only do they provide a sizable amount of information on various endpoints of interest (i.e., incident infection and risk behaviors), but they also have carefully addressed potential alternative explanations for their reported findings. POTENTIAL OUTCOMES At the outset, it is important to recognize that the effects of needle exchange programs can be viewed from a number of different perspectives. Some of these perspectives involve outcomes relevant to improving the health status of injection drug users, and others reflect community-level concerns regarding potential negative effects that may be associated with the implementation of such programs. The following section identifies the outcome domains that are relevant to those distinct perspectives and are most germane to the panel's task of assessing the effects of needle exchange programs. Possible Positive Outcomes Needle exchanges are established in order to: (1) increase the availability of sterile injection equipment and (2) at the same time, remove contaminated needles from circulation among the program participants. Operation of the exchange, then, is expected to result in a supply of needles with reduced potential for infecting program participants with HIV and also to reduce sharing between individuals because of easier access to clean needles for any program participant. Typical exchanges also maintain such services as education concerning risk behaviors, referral to drug treatment programs (a step toward eliminating the route for all infection), and distribution of condoms. These measures offer independent prospects for reducing the spread of HIV. Appraisal of the success of a needle exchange program may involve measuring, for example, the numbers of needles exchanged; the cleanliness of circulating needles; the prevalence and incidence of HIV and other needle-borne diseases; referrals to drug treatment programs; enrollments in treatment programs; and changes in the risk behaviors of needle exchange participants. An observed pattern of favorable outcomes would reflect health benefits from the operation of the program. Possible Negative Outcomes The possibility of negative results from needle exchange program operations also demands attention. One possible negative outcome is an increase
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach TABLE 7.1 Possible Outcomes and Expectations of Successful Needle Exchange Programs Possible Positive Outcomes: Possible Negative Outcomes: Reduction in pool of infected needles Increase in drug use among needle exchange program clients Reduction in drug-related risk behavior Increase in new initiates to injection drug use Reduction in sexual risk behavior Increase in drug use in wider community Increase in referrals to drug abuse treatment Increase in number of contaminated needles unsafely discarded (e.g., on streets) Reduction in new infections among client population in the number of improperly discarded used needles. Another possibility is that the issuance of injection equipment, condoned by government, will "send a message" undercutting efforts at combatting illegal drug use and will promote more drug use (with more attendant HIV incidence). A third possible negative outcome is that needle exchanges will lower the perception of risk of injection drug use and thus attract more users to inject drugs and to other forms of illegal drug use. Appraisal of the success of a needle exchange program, then, should also attend to measures of these possible negative outcomes. An observed pattern of negative outcomes would weigh against the idea that needle exchange programs are beneficial. Assessment of the effects of needle exchanges involves the simultaneous consideration of a number of intended positive and unintended negative outcomes (Table 7.1). Ideally, a successful exchange program would reduce the risk of new infection among injection drug users without increasing drug use and health risks to the public. THE PANEL'S APPROACH TO THE EVIDENCE The purpose of this section is to clearly explain the panel's perspective in assessing the effectiveness of needle exchange programs. We first briefly review the basis for the traditional review procedures. We then outline the argument for a different approach—one that examines the patterns of evidence in order to assess effectiveness. The Traditional Approach: Considering the Preponderance of the Evidence Traditional reviews of experimental analysis search for studies with well-controlled research designs. By well-controlled designs, we mean ones
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach that can substantially protect against the introduction of systematic influences (i.e., bias) other than the intervention condition under consideration. High ratings on credibility are usually given to comparative designs that involve: (1) random assignment of participants to conditions (i.e., needle exchange program versus "usual services"); (2) minimal attrition of participants from being measured; (3) measurement procedures that minimize the role of response biases; and (4) sufficient statistical sensitivity (i.e., statistical power). It is unlikely that evaluations of needle exchange programs will ever be carried out with ideal controls that warrant high confidence in the conclusions that can be drawn from a single definitive study. There are at least two broad reasons for this: (1) multiple actions generally are initiated in a given community setting, making it difficult to separate the effects of a needle exchange program from those of other prevention efforts by studying time trends and (2) the development of a comparative research design that relies on random assignment of individuals to receive needle exchange program services (or not) has technical, ethical, and logistical difficulties. Given these limitations, it seems reasonable to explore alternative means of assessing the credibility of the evidence's underlying claims about the effectiveness of needle exchange programs. Before doing so, however, it is useful to examine how previous research reviews have attempted to incorporate the traditional emphasis on design-induced control. Two reviews were commissioned by the federal government and published in 1993: one by the U.S. General Accounting Office (1993) and one by the University of California at San Francisco (Lurie et al., 1993). Prior to 1993, a number of other studies were published (Des Jarlais et al., 1985; Stimson et al., 1988). A close examination of the manner in which these studies were conducted strongly suggests their reliance on the quality of the evidence in individual studies, which is based on the strength of their research designs. The language of the assessments also reflects the expectation that, when they are taken as a collective across studies, even though the designs are less than ideal, the preponderance of evidence will weigh in favor of or against a definitive conclusion about needle exchange programs. Taken together, these studies tend to suggest that needle exchange programs are either neutral or positive in terms of potential positive effects and that they do not demonstrate any potential negative effects. However, each study's conclusions are often less than firm because of its methodological limitations. An Alternative Approach: Looking at the Patterns of Evidence When the designs of a group of studies are limited, little inferential clarity is gained by looking at the preponderance of evidence, even if it
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach converges across all available studies. At a minimum, there must be a sufficient number of higher-quality (i.e., high-credibility) studies within the pool of studies to assess whether the evidence from the lower-quality studies is biased in a particular fashion. Rationale For well-designed interventions with well-designed experimental assessment procedures, examining each outcome one at a time is obviously justifiable on statistical and logical grounds. However, in light of the fact that most studies that have attempted to assess the effectiveness of needle exchange programs have limited study designs and that there are serious practical constraints associated with conducting a randomized control trial, some may conclude that it is impossible to ever determine whether needle exchange programs are effective. In the panel's view, however, such a conclusion is both poor scientific judgment and bad public health policy. Indeed, to adopt the position that evidence short of a randomized trial is useless amounts to denying the possibility of learning from experience—which, though often difficult, is not impossible. In many areas of social sciences and public health research, the so-called definitive study—a randomized control experiment (that is, a randomized double-blind placebo controlled trial)—is an ideal that cannot be implemented. For example, it is unethical to consider use of a clinical trial design to show that smoking causes lung cancer (Hill, 1965). Scientific judgment develops instead through a series of studies using cross-sectional retrospective and prospective designs, in which later research avoids the flaws of earlier work but may introduce problems of its own. The improbability of being able to carry out the definitive study of the effects of certain HIV and AIDS prevention programs, including needle exchange programs, does not necessarily preclude the possibility of making confident scientific judgments about the effects of such prevention programs. As A. Bradford Hill (1965:300), one of this century's foremost biostatisticians, commented three decades ago: All scientific work is incomplete—whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time. Sooner or later there comes a time for decision on the basis of evidence in hand. In the case of the efficacy of needle exchange programs, urgency is added because the disease in question—AIDS—is fatal, is contagious, and has been seen to spread rapidly in various settings. Previous assessments
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach of individual studies (as well as the panel's own) did not rate them as highly conclusive, because none of them used the gold standard of randomized controlled research designs. The panel therefore elected to rely on an approach that assesses the pattern of evidence in determining the effects of these HIV and AIDS prevention programs rather than relying on a preponderance of evidence approach. In this approach to assessing the effects of needle exchange programs and the credibility of evidence surrounding a needle exchange program, we look at the consistency of the pattern of evidence that is available from multiple data sources about the same program. Taking this approach greatly expands the depth and breadth of the evidentiary base, because we try to understand the relationships among the parts of the intervention model, the process, and their outcomes. Rather than interpreting the effects of the intervention on individual outcomes, in isolation, the pattern of evidence approach considers interrelated conditions, such as intermediate outcomes (Cordray, 1986). For example, consider the evaluation of a needle exchange program that reveals a reduction in new HIV infections over time among injection drug users who used the program. By traditional standards, this design would be classified as relatively weak because there is no control or comparison condition. Without further information, it is not possible to confidently conclude that the introduction of the needle exchange program is responsible for the observed decline on the basis of this one piece of evidence (the observed decline) alone. Ruling In Plausibility By examining whether certain required conditions were present, it is possible to probe the plausibility that the needle exchange program was responsible, at least in part, for the reduction. This type of assessment requires the specification of a series of if-then propositions. That is, if there is a real connection between the introduction of the needle exchange program and the observed decline in new infections, then a series of conditions must be present in order to increase confidence in the conclusion that the program is at least partially responsible for the observed outcome. The conclusion that the needle exchange program is plausibly connected to the decrease in new HIV infections is more credible if there is evidence that, as the putative causal agent, it was actually present in the community. This means that there must be an empirical pattern of evidence that, in effect, rules in its plausibility. Programmatically, the pattern of evidence might include: information that the needle exchange program was established;
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach data that it exchanged a sufficient number of needles; data that it provided needles to a substantial enough portion of the injection drug users in the community; data that those who used the needle exchange reduced their level of drug-use risk behaviors (e.g., sharing, use of bleach); and data that those who used the needle exchange most intensively show a greater level of risk reduction. The argument that undergirds this approach is that programs have a structure and mechanisms that establish a logical pattern of expectations that can be tested empirically. To the extent that the empirical evidence supports these propositions, the plausibility that the needle exchange program was responsible for the observed change should increase. That is, the plausibility increases through repeated assessments. As a simple example, if there is a reduction in HIV incidence but the needle exchange program failed to exchange a single needle, it is not reasonable to conclude that the needle exchange program was responsible for the decline, regardless of the strength of the design underlying the HIV incidence data. However, through multiple assessments, involving a logical network of evidence, it may be possible to derive a portrait of the plausibility that the needle exchange program is implicated in the change process. Ruling in the plausibility that the needle exchange program is a causal agent, through empirical assessment, is only half the story. It is still possible that other features of the program or research process contain biases that affect the HIV incidence. In traditional discussions of causal analysis, the notion of excluding (or rendering implausible) rival explanations has been the hallmark of competent experimental analysis. To the extent that repeated efforts to probe the results fail to disconfirm the plausibility that the intervention was at least partially responsible, its plausibility should be enhanced. Therefore, an assessment of the pattern of evidence not only entails ruling in the plausibility that the needle exchange program is a causal agent, but also requires ruling out plausible alternative explanations. The Panel's Synthesis The panel analyzed the patterns of evidence from five sources: two evaluations of the research published before 1993, the findings of studies published since 1993, and two sets of studies that provide the best available detailed account of how needle exchange programs impact risk behaviors and viral infections—one on New Haven, the other on Tacoma. The process of selecting studies for detailed examination involved a comprehensive analysis of the research findings of individual needle exchange and bleach distribution projects. The panel generated a list of published
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach papers and presentations on needle exchange evaluation projects in the United States, Canada, and Europe. A meeting was held to judge which reports included data that might be used in a review. The projects were subsequently grouped by city and divided among panel members so that each city project had two independent reviewers. The studies from each city were reviewed, annotated on a formal evaluation form, and then discussed with the full panel at a subsequent meeting. Following this review, at a separate meeting, the panel decided to limit itself to studies conducted in the United States, because the legal and cultural environments of other countries are sufficiently different to raise questions about whether data are applicable to the United States. Two U.S. cities, New Haven and Tacoma, were found to have a sufficient number of data published from a variety of perspectives (e.g., incident infection, behavioral risk) to warrant inclusion in this review. Various criteria were used in deciding to pursue the New Haven and Tacoma sets of studies. Consistent with the logic of the patterns of evidence approach, the first criterion applied in selecting studies was that the site or project had to have been comprehensively studied. That is, there had to be empirical evidence establishing that the needle exchange program was operational, that the mechanisms of the exchange process had been studied, and that there was an estimate of HIV incidence or, as in the case of New Haven, a proxy measure. The level of activity in the prevention environment can make it difficult to isolate the influence of the needle exchange program. A second criterion was that, in the sites and projects selected, the needle exchange program had to be the predominant (if not the only) intervention ongoing at the time of the assessment. This criterion implies a selection process that focuses on high-contrast sites (i.e., the needle exchange program intervention dominates prevention activities in the area), thus yielding estimated effects of needle exchange that cannot readily be attributed to other prevention activities reaching the program participants. U.S. GENERAL ACCOUNTING OFFICE REVIEW In late 1991, the House Select Committee on Narcotics Abuse and Control requested that the U.S. General Accounting Office carry out a review of the effectiveness of needle exchange programs.1 Procedure GAO researchers carried out an extensive review of the literature to identify empirical evaluation studies that had appeared in refereed or peer-reviewed
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach journals. They conducted site visits to programs located in Tacoma, Washington, and New Haven, Connecticut. Their review identified a total of 20 published studies and 21 abstracts on evaluations of needle exchange programs originating from nine distinct research projects, all but one of which (the Tacoma study) involved programs outside the United States. Among the nine research projects were one from Australia, one from Canada, two from the Netherlands, one from Sweden, and three from the United Kingdom. The GAO team developed a list of eight relevant outcome measures: (1) rate of needle sharing; (2) prevalence of injection drug use; (3) frequency of injection; (4) rate of new HIV infections; (5) rate of new entrants to injection drug use; (6) incidence rate of other blood-borne infections; (7) rate of other HIV risk behaviors; and (8) risk to the public's health. They also identified three methodological criteria that had to be satisfied before findings could be considered: (1) the findings had to have been published in a scientific journal or government research monograph; (2) they had to have reached statistical significance; and (3) the reported effects of the needle exchange program could not have been attributed by the authors to any other source. Of the eight listed outcome measures, only three outcomes met the methodological standard of evidence set by the GAO team: (1) rate of needle sharing, (2) prevalence of injection drug use, and (3) frequency of injection. The GAO team summarized descriptive information, whenever it was available, on the ability of needle exchange programs to reach out to injection drug users and refer them to drug treatment and other health services. Results Tables 7.2 and 7.3 summarize the GAO findings. Regarding the potential positive outcomes, of the nine research projects reviewed, two reported a reduction in needle sharing, and a third reported an increase. It should be noted that the increase in sharing by needle exchange participants resulted from their passing on more used injection equipment (Klee et al., 1991); this finding was not replicated in a follow-up report by the same investigator (Klee and Morris, 1994). The earlier finding from that study appears to have been a transient effect that occurred before the needle exchange programs in the area reached full operation; that is, needle exchange participants were being used as a source of needles among their respective networks of injection drug users (Klee and Morris, 1994). The researchers concluded, moreover, based on the data available from six of the nine projects, that the needle exchange programs were successful in reaching injection drug users and providing a link to drug treatment and other health services. Regarding potential negative outcomes of needle exchange programs,
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach TABLE 7.2 GAO Review: Results of Needle Exchange Program Study Projects Project Number by Country Needle Sharing Prevalence of Injection Frequency of Injection Drug Use Australia 1 a Canada 2 Netherlands 3 a 4 Reduction Reduction Sweden 5 United Kingdom 6 7 Reduction 8 Increase United States 9 Reduction a a GAO reported these as showing no increase; however, a review of the original studies indicates that no statistically significant findings were reported for the outcome measure assessed. SOURCE: Adapted from Needle Exchange Programs: Research Suggests Promise as an AIDS Prevention Strategy (U.S. General Accounting Office, 1993:7). all five projects that reported findings on injection drug use by program participants—four on frequency of injection and one on prevalence of use—found that use did not increase. (Note that three of these findings did not reach statistical significance.) This led GAO to conclude that ''some research suggests programs may reduce AIDS-related risk behavior" (p. 6) and "most projects suggest that programs do not increase injection drug use" (p. 8). GAO reported that there was sufficient evidence to suggest that needle exchange programs "hold some promise as an AIDS prevention strategy" (p. 4). In summary, the GAO report, which was the first government report to evaluate needle exchange programs, concluded that such programs hold promise as interventions to limit HIV transmission. The criteria for assessing the validity of the study findings and for including reports in the review were quite stringent. In particular, the criterion of statistical significance means that studies that showed no difference in the frequency of injection or needle sharing were excluded. Therefore, the argument that needle exchange programs cause no harm is not fully characterized because studies
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach TABLE 7.3 GAO Review: Needle Exchange Program Outcomes Measured and Reported Project Number by Country Attracted Injection Drug Users Not in Treatment Referred Injection Drug User to Drug Treatment Referred Injection Drug User to Other Health Services Australia 1 Canada 2 Yes Yes Netherlands 3 4 Yes Sweden 5 Yes Yes United Kingdom 6 Yes 7 Yes Yes Yes 8 United States 9 Yes Yes SOURCE: Adapted from Needle Exchange Programs: Research Suggests Promise as an AIDS Prevention Strategy (U.S. General Accounting Office, 1993:10). with high level of statistical power that showed no difference were excluded. UNIVERSITY OF CALIFORNIA REPORT In September 1993, a second government report, The Public Health Impact of Needle Exchange Programs in the United States and Abroad , was published by the University of California for the Centers for Disease Control and Prevention (CDC). This report consists of a summary volume with two supporting volumes and addresses a number of the questions that this panel was asked to address. Procedure The University of California report was the work of a team of 12 individuals with expertise in clinical medicine, nursing, psychology, anthropology, sociology, cost-benefit modeling, and epidemiology. None of the team
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach to injection drug users. However, the record shows little evidence in support of these concerns. There is no credible evidence to date that drug use is increased among participants as a result of programs that provide legal access to sterile equipment. (Long-term effects are necessarily not yet known, providing a reason for continued monitoring for potential negative effects.) The available scientific literature provides evidence based on self-reports that needle exchange programs: do not increase the frequency of injection among program participants and do not increase the number of new initiates to injection drug use. The available scientific literature provides evidence that needle exchange programs: have public support, depending on locality, and have public support that tends to increase over time (where trend data are available). The high level of concern about potential negative effects of needle exchange and bleach distribution programs cannot be ignored, despite the paucity of supporting evidence. Communities wracked with drug abuse and addiction, AIDS, crime, and poverty may well resent the institution of needle exchange and bleach distribution programs, seeing the programs as a wholly inadequate response to the key problems. Attention to comprehensive responses to the drug epidemic is clearly important, especially the expansion of drug treatment to make it more available. Needle exchange programs should be regarded as a public health promotion and disease prevention strategy that fits within the broader harm reduction approach to public health. It is essential that prevention programs (including initiation of needle exchange programs) must vary regionally and locally to reflect those infected or at risk in any area. Thus, although the panel supports the use of needle exchange and bleach distribution programs as part of a nationwide HIV prevention strategy, it is absolutely critical that their use should be driven by the nature of the epidemic in different locales. Recommendations The specific charge to this panel was to examine the effectiveness of syringe exchange and bleach distribution as methods of reducing HIV transmission.
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach This necessarily led to some consideration of other methods of reducing HIV transmission. Reducing drug use would serve to reduce HIV transmission as well as to achieve other important social and public health goals. Comprehensive drug treatment is one important way to reduce drug use. However, (1) treatment, especially comprehensive treatment, is inadequately available; (2) treatment does not work for all individuals who enter it; and (3) not all drug abusers currently are willing ("wish") to enter treatment. For all of these reasons, researchers have explored the efficacy of more limited programs, such as needle exchange and bleach distribution, as a means of reducing the risk of HIV infection by providing users not able to undertake drug treatment access to uncontaminated injection equipment. Based on a comprehensive review of the research literature, the panel concludes that well-implemented needle exchange programs can be effective in preventing the spread of HIV and do not increase the use of illegal drugs. Hence, we recommend that: The Surgeon General make the determination called for in P.L. 102-394, section 514, 1993, necessary to rescind the present prohibition against applying any federal funds to support needle exchange programs. Observe that the panel does not recommend a mandated national program of needle exchange and bleach distribution. As documented in this report, regional variation in prevalence of HIV infection, the extent and kind of drug use, the presence of other AIDS programs, operational characteristics of existing needle exchange programs, and the attitudes and needs of local communities all influence the potential effects of needle exchange programs and militate against such a mandate. The recommendation is to allow communities that desire such programs to institute them, using resources at their disposal and unencumbered by the specific funding handicap that is now in place. If needle exchange programs become available tools of public health and disease prevention, certain implementation measures become desirable. In particular, the panel recommends that: Local community members (e.g., police, church, treatment providers, pharmacists, local public health authorities) should be involved in determining whether such programs should be implemented locally and how they should be institutionalized. Attention must be given to the development of site-specific programs that are community based, culturally sensitive, and capable of demonstrating respect for the concerns of the communities in which they are to
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach be based. The importance of flexibility and community control is strongly emphasized. Appropriate health agencies should make available technical assistance and relevant epidemiologic data to local organizations and groups within the communities to assist them in making informed decisions about needle exchange and bleach distribution programs. Needle exchange programs should promote HIV prevention not only by providing sterile equipment, but also by means of education, drug treatment referral, and materials, including bleach, alcohol pads, and condoms. Needle exchange programs should make special efforts to reach and retain hard-to reach subgroups of injection drug users, such as young injection drug users and women. The National Institutes of Health, the Centers for Disease Control and Prevention, and the Agency for Health Care Policy and Research should support evaluation research examining the programs and the key outcomes, including HIV risk behavior and reduced HIV transmission. The panel further recommends that in meeting the need for increasing the treatment capacity, as described above, Incremental funds for needle exchange programs and other AIDS prevention strategies should be appropriated but should not be taken from resources now supporting drug treatment programs. In addition, such a diversion of funds would be unwise because drug treatment programs have been shown to be effective in treating the underlying disorder of drug abuse and can be effective in curtailing HIV risk behaviors. Moreover, for many program participants, needle exchange and bleach distribution programs have been found to serve as a bridge to drug treatment for many needle exchange program clients. Indeed, the panel further recommends that: The appropriate legislative bodies should enact legislation (and should appropriate monies) to increase drug treatment capacity and establish better links between treatment and AIDS prevention programs that target injection drug users. Finally, the panel recommends that: The National Institutes of Health (e.g., National Institute on Drug Abuse) and the Centers for Disease Control and Prevention should support research that evaluates the effect of needle exchange and bleach distribution
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach programs on the severity of abuse and addiction among needle exchange and bleach distribution program participants. A better monitoring system should be established for assessing long-term societal changes in drug use at the community level due to needle exchange programs. NOTES 1. Specifically the GAO was requested to: (1) review the results of studies addressing the effectiveness of needle exchange programs in the United States and abroad; (2) assess the credibility of a forecasting model developed at Yale University that estimates the impact of a needle exchange program on the rate of new HIV infections; and (3) determine whether federal funds can be used in support of studies and demonstrations of needle exchange programs. 2. The U.S. project sites were Berkeley, California; Boston, Massachusetts; Boulder, Colorado; New Haven, Connecticut; New York City, New York; Portland, Oregon; San Francisco, California; Santa Cruz, California; Seattle, Washington; and Tacoma, Washington. Sites abroad included: Montréal, Toronto, and Vancouver (Canada); Amsterdam, the Netherlands; and London, England. 3. To derive the estimate of the relative impact, Kaplan and his colleagues developed a model based on a circulation theory. The basic idea is that each time an infected needle is removed from circulation among a population of injection drug users and replaced with a sterile needle, the risk of infecting some member of that population is decreased. This model was based on a two-state continuous time Markov process and assumed that uncontaminated needles become infected at a rate that does not change over time, and infected needles become uncontaminated at another rate that also does not change over time. Under these assumptions, a formula was developed for the expected proportion of circulating needles that were infected. This formula involved these rates and the mean circulation time. Data from the Syringe Tracking System developed for the New Haven project were used to estimate these rates as well as the mean circulation times of needles before and after the initiation of the needle exchange program. These estimates and formulas were used to determine that the relative reduction in the expected proportion of circulating needles that were infected was 33 percent. 4. In order to compute absolute reduction in incidence, estimates of the baseline HIV incidence rate before the initiation of the needle exchange program were required. This was determined by introducing some additional modeling assumptions concerning the dynamics of the epidemic. These calculations, together with additional assumptions about the proportion of infections among injection drug users resulting from needle sharing as opposed to sexual transmission, estimated that between 1 and 4 HIV infections were prevented per 100 injection drug users per year. This range of the estimated number of infections averted was derived by two methods: (1) the equilibrium method and (2) the back calculation method (involving 7 years of AIDS incidence data for New Haven). The equilibrium method estimates 1.2 to 2.8 averted infections; the back calculation method estimates 1.07 to 3.73
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach (assumes 30 percent of infections are sexually transmitted) or 0.92 to 3.2 (assumes 40 percent derived from sexual exposure) averted infections. 5. In a footnote, Heimer et al. (1993) explain that, for demographics to account for these results, assuming that needle exchange programs have no effect, the contribution to the overall prevalence rates for earlier and late time periods should be proportionate to the fractional size of each group at each time point. Solving these two equations reveals the impossible value for white participants. Therefore, they reject the plausibility of this explanation. 6. The community-based organization submits monthly reports to the health department detailing syringe exchange activities; somewhat less detailed reports are provided by the health department pharmacy. These were used to estimate numbers of syringes, client contacts, referrals, and prevention materials distributed January to November 1994. 7. A program of stimulated case reporting of hepatitis in the county has resulted in approximately 50 percent of all hepatitis being reported in Pierce County, compared with about 17 percent nationwide (Alter et al., 1987). REFERENCES Alcabes, P., E.E. Schoenbaum, and R.S. Klein 1993 Correlates of rate of decline of CD4+ lymphocytes among intravenous drug users infected with human immunodeficiency virus. American Journal of Epidemiology 137:989-1000. Alter, M.J., A. Mares, S.C. Hadler, and J.E. Maynard 1987 The effect of underreporting on the apparent incidence and epidemiology of acute viral hepatitis. American Journal of Epidemiology 125:133-139. Alter, M.J., S.C. Hadler, and H.S. Margolis 1990a The changing epidemiology of hepatitis B in the United States. Journal of the American Medical Association 263:1218-1222. Alter, M.J., S.C. Hadler, and F.N. Judson 1990b Risk factors for acute non-A, non-B hepatitis in the United States and association with hepatitis C virus infection. Journal of the American Medical Association 264:2231-2235. Bachman, J.G., L.D. Johnston, and P.M. O'Malley 1990 Explaining the recent decline in cocaine use among young adults: Further evidence that perceived risks and disapproval lead to reduced drug use. Journal of Health and Social Behavior 3(June):173-184. Bruneau, J., F. Lamothe, E. Franco, N. Lachance, J. Vincelette, and J. Stoto 1995 Needle Exchange Program (NEP) Attendance and HIV-1 Infection in Montréal: Report of a Paradoxical Association. Abstract for International Conference on the Reduction of Drug Related Harm, Palazzo dei Congressi, Florence, Italy, March 26-30. Carman, R.S. 1979 Motivations for drug use and problematic outcomes among rural junior high school students. Addictive Behaviors 4:91-93. Clayton, R.R., and C.G. Leukefeld 1994 Drug Use and Its Progression to Drug Abuse and Drug Dependence: Implications for Needle Exchange and Bleach Distribution Programs. Paper commissioned by
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Preventing HIV Transmission: The Role of Sterile Needles and Bleach Stimson, G.V., J. Keene, N. Parry-Langdon, and S. Jones 1991 Evaluation of the Syringe Exchange Programme in Wales, 1990-91: Final Report to Welsh Office. Centre for Research on Drugs and Health Behaviour. December. U.S. General Accounting Office 1993 Needle Exchange Programs: Research Suggests Promise as an AIDS Prevention Strategy. (GAO/HRD-93-60). Washington, DC: U.S. Government Printing Office. van Ameijden, E.J.C., J.A.R. van den Hoek, and R.A. Coutinho 1993 A Major Decline in Risk Behavior Over 6 Years Among IDUs. Abstract WS-C21-2 in Final Program and Abstracts of the IX International Conference on AIDS, Berlin. van Ameijden, E.J.C., J.A.R. van den Hoek, C. Hartgers, and R.A. Coutinho 1994 Risk factors for the transition from noninjection to injection drug use and accompanying AIDS risk behavior in a cohort of drug users. American Journal of Epidemiology 139:1153-1163. Watters, J.K. 1994 Trends in risk behavior and HIV seroprevalence in heterosexual injection drug users in San Francisco, 1986-1992. Journal of Acquired Immune Deficiency Syndromes 7:1276-1281. Watters, J., and Y. Cheng 1991 Syringe Exchange in San Francisco: Preliminary Findings. Abstract ThC 99 in Final Program and Abstracts of the VII International Conference on AIDS, Florence. Watters, J.K., M.J. Estilo, G.L. Clark, and J. Lorvick 1994 Syringe and needle exchange as HIV/AIDS prevention for injection drug users. Journal of the American Medical Association 271(2):115-120.
Representative terms from entire chapter: