8 Directions for Future Research

As this report demonstrates, needle exchange programs have been shown to have the ability to retard the spread of HIV infection among the injection drug users who participate in them. It is also true that bleach distribution programs offer promise of being useful in a similar way. Improving the effectiveness of HIV and AIDS prevention programs such as needle exchange and bleach distribution programs is an important and valid public health goal. Such improvement would be much easier to accomplish if the knowledge base were broader and more secure.

On the basis of our review of the epidemiologic data, program characteristics, community views, legal constraints, and the impact of the programs on an array of outcomes (both positive and negative), the panel notes that there is substantial room to expand and improve the current state of knowledge. Several areas must be explored further to enhance understanding of the dynamic process of managing the myriad aspects of the HIV epidemic in the United States and limiting the imminent danger it poses for the public health. In this chapter we briefly discuss some of the most salient areas in which further study has the potential to more effectively limit the spread of this deadly infectious viral agent. We note, however, that our intent is not to set priorities for the funding of needed research, but rather to point out research issues that need to be addressed to enhance the current knowledge base.



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Preventing HIV Transmission: The Role of Sterile Needles and Bleach 8 Directions for Future Research As this report demonstrates, needle exchange programs have been shown to have the ability to retard the spread of HIV infection among the injection drug users who participate in them. It is also true that bleach distribution programs offer promise of being useful in a similar way. Improving the effectiveness of HIV and AIDS prevention programs such as needle exchange and bleach distribution programs is an important and valid public health goal. Such improvement would be much easier to accomplish if the knowledge base were broader and more secure. On the basis of our review of the epidemiologic data, program characteristics, community views, legal constraints, and the impact of the programs on an array of outcomes (both positive and negative), the panel notes that there is substantial room to expand and improve the current state of knowledge. Several areas must be explored further to enhance understanding of the dynamic process of managing the myriad aspects of the HIV epidemic in the United States and limiting the imminent danger it poses for the public health. In this chapter we briefly discuss some of the most salient areas in which further study has the potential to more effectively limit the spread of this deadly infectious viral agent. We note, however, that our intent is not to set priorities for the funding of needed research, but rather to point out research issues that need to be addressed to enhance the current knowledge base.

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach RESEARCH ON PROGRAM EFFECTIVENESS Needle Exchange Evaluation As illustrated by the literature reviewed in Chapter 7, previous evaluation studies have provided valuable insights into issues to be considered for future research endeavors. Such issues include (but are not limited to): categorization of exposure to the intervention condition (ever/never, secondary exchangers); measurement of alternative sources of sterile syringes other than needle exchange programs (e.g., pharmacies, diabetics); opportunistic comparison groups; eligibility requirements; temporal associations of participation program and HIV seroconversion; accounting for alternative modes of HIV transmission; and consolidation and coordination of program effects. A discussion of these issues follows. Categorization of Exposure to Intervention Condition Many studies have simply compared ''ever" versus "never used" a needle exchange, with no provisions to allow the researcher to distinguish between different intensity (or frequency) of program exposure across participants. This creates a problem because most needle exchange reports to date identify a substantial proportion of needle exchange participants who have used the program only once. To consider the single-time users similar to frequent users, but different from never users, dilutes any potential effect due to program participation. At a minimum, analyses of the effects of needle exchange program use should stratify by the frequency with which the program is used, to allow for an assessment of a dose response. At the other extreme, a small proportion (e.g., >25 percent) of program participants have been known to exchange extraordinarily large numbers of needles (e.g., in Tacoma, Chicago, and San Francisco), unlike the single-time users who are not interested in continuing participation for undetermined reasons. Regular low or moderate users who are engaged in personal risk reduction are unlike the high-frequency users who exchange large numbers and are likely to be secondary exchangers . This phenomenon raises serious concerns about the common practice of using means as a summary statistic in the analyses of program effect. Employing this method equates all exchangers and may lead to masking trends in subgroups. Therefore, it is important to delineate subgroups and define risks accordingly. The role of secondary exchangers is controversial because a small portion of exchange users obtains a large portion of syringes distributed by the programs. The number of syringes exchanged by these participants typically exceeds the number of syringes that would be used by a single individual. Although this could lead to individuals making money to support

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach their drug habit, it also could facilitate the much wider dissemination of sterile syringes, particularly in areas in which limited program hours allow only a small number of injection drug users to be served directly by the program. More research on secondary exchange is warranted. Measurement of Alternative Sources of Sterile Syringes To properly measure sources of sterile syringes, asking injection drug users only if they use or do not use the needle exchange program is insufficient. Other extant sources of sterile syringes can impact enrollment and measurement of outcomes from the program. Prior studies in Baltimore (Gleghorn, in press) show that about half of injection drug users had sterile sources of needles prior to the opening of the needle exchange program, which were primarily from diabetics and pharmacies in a city with a paraphernalia—but no prescription —law. If needle exchange programs differentially attract people with nonsterile street sources but not those who already have sources of sterile needles, then, when comparing participants and nonparticipants, an evaluation study might show no relative reduction in HIV incidence resulting from program participation. This may partially explain the lack of significant findings in the Amsterdam case-control study (in which nonparticipants had access to unrestricted pharmacy sales) and appears to contribute, in part, to the findings of the Montréal needle exchange program (see Appendix A). Evaluations of needle exchange programs should collect and analyze information about sources of needles and syringes for all study participants, regardless of their program participation status. Community-Based Studies Some studies to date have collected data from programs on needle exchange participants and then sought data on a group of nonparticipants to generate comparisons. However, the different settings in which data are collected are likely to raise concerns about differential bias of interviewers and recall among participants. The panel recommends the use of prospective community-based studies of injection drug users—independent of the operation of needle exchange programs—while gathering information on program use. Comparison groups of nonparticipants might nevertheless have contact with program users and even obtain needles from the program, although they are not directly enrolled. Therefore, information on contacts with persons who use needle exchange programs and are the recipients of secondary exchange should be collected and incorporated into the analysis.

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach Appropriate Selection of Respondents Studies that follow injection drug users over time should not restrict themselves to only the highest-risk users. Although this strategy would seem to efficiently select persons at highest risk of seroconversion and thereby make evaluations statistically efficient, a drawback of this strategy is that such selection may be subject to effects of regression to the mean (i.e., the highest-risk persons have nowhere to go except down in terms of behavioral and HIV risk). Analyses of offsetting trends using person-time analysis, which uses time intervals rather than individuals as units of analysis, can mask these offsetting trends; they should be maintained in analysis to consider these possible effects. Temporal Association of Participation in Programs and HIV Seroconversion The incubation period for HIV seroconversion is generally within 2 weeks to 3 months. Within prospective epidemiologic studies, the date of seroconversion is generally calculated as the midpoint between the last seronegative and the first seropositive serological test visit. This estimation procedure creates a window of uncertainty that needs to be carefully considered in evaluation studies (see Appendix A). Specifically, if an injection drug user is a recent enrollee in a needle exchange program and seroconverts within the next several months, it will be difficult to determine whether the seroconversion can be ascribed to activities engaged in prior or subsequent to use of the exchange program. Particular care needs to be exercised in establishment of inferences related to individuals who seroconvert soon after enrollment in a needle exchange program. Accounting for Alternative Risk Behaviors Needle exchange and bleach distribution programs are intended to reduce the risk of HIV and other blood-borne infections due to sharing of contaminated syringes. However, the use of sterile needles and bleach disinfection alone does not have an impact on risks from indirect sharing (e.g., sharing cookers) or sexual risk behaviors. As noted in Chapter 1, sexual transmission is not uncommon among injection drug users. Unless significant efforts to determine the risk associated with indirect sharing and more efficient sexual risk reduction strategies are developed within the context of such programs, the effect of needle exchange programs on HIV incidence is likely to be somewhat limited. The needle exchange research community should bear in mind that there are multiple routes of transmission, each with multiple transmission mechanisms,

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach and that direct needle sharing constitutes only one of many potential sources of transmission. Unless needle exchange programs consistently provide a full range of sterile equipment and adequate education regarding these risky behaviors, it is likely that some transmission stemming from these other practices will continue. To date, no studies to quantify the risk associated with these other behaviors in relation to direct needle sharing are available. In short, the effect of needle exchange on HIV incidence is likely to be confounded with other sources and modes of transmission. At best, these considerations point to the need for needle exchange programs to institute multidimensional approaches to prevention and not simply rely on distribution and exchange of needles. Providing sterile needles and syringes is necessary but insufficient to adequately address the problem of HIV transmission. Therefore, the relative effects of different components of needle exchange programs that target different risk behaviors associated with the different transmission routes (sexual risk versus sharing of contaminated injection equipment) need to be studied. Consolidation and Coordination of Program Effects What is learned about program effectiveness at one site may be of value at another; sharing and consolidating information increases its value. It is also essential to develop standard terms and a common format for record-keeping, as a way to ensure consistency in the collection of data from different programs at different sites. Consistency in data collection makes it possible to supply program operators and evaluators with more valid feedback about program effectiveness: what works in Denver may not work in Miami, but, without consistent information, it may not be possible to analyze the results of program evaluations across sites. In funding considerations, coordination is also essential. The efficiency of needle exchange and bleach distribution programs would benefit from some centrally supplied funding and some central coordination of what could be a primarily collaborative enterprise. This could make provision for more reliable and swift learning from the experiences of programs already in operation. Program Characteristics Most evaluation research to date has focused on program effectiveness in isolation. Needle exchange and bleach distribution programs vary considerably in their characteristics (as noted in Chapter 3) and their effectiveness. Their success depends in part on the choices they make in setting their hours of operation, their location(s), their eligibility rules, and their

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach exchange policies. Some programs insist on one-for-one exchange, and others do not. Some programs limit the number of needles that may be exchanged at one time, and others do not. Each of these policies has pros and cons, but we know too little about them, in terms of what balance is optimal in maximizing gains, minimizing harm, and contributing to the ultimate goal of the program—prevention of HIV transmission. Also, as Chapter 2 describes in detail, the aims of needle exchange and bleach distribution programs are broader than simply providing sterile needles to injection drug users. Other goals include linking users to needed health care and social services, providing drug abuse counseling, and facilitating entry into drug treatment. Research on how to improve these ancillary services is virtually nonexistent and should be pursued. The most effective ways to pursue these goals presumably depends in part on the characteristics of the participants, such as age, ethnicity, education, drug-using career, and socioeconomic status. Identification of program characteristics that enhance or inhibit effectiveness is needed. The limited available research on the organizational characteristics of needle exchange programs and case studies presented in Chapter 3 hints at specific operational characteristics that may facilitate program effectiveness—for example, user-friendliness (see Stimson et al., 1988). Evaluation research in this area of study would also benefit from adopting programmatic research strategies that acknowledge the need for feeding back information to program administrators to allow rational modification of procedures and operational characteristics. This type of iterative research process attempts to identify optimal procedures for maximizing the overall effectiveness of programs or identifying problematic components resistant to effectiveness modification. Quality assurance programs are witness to the value of systematic internal research with feedback as a method for improving the operations of almost any kind of organization. In addition to examining the relative effects of different operational characteristics of programs (such as staffing, location, hours of operation, program policies) and various combinations of ancillary services on traditional outcomes (e.g., risk behaviors, infection rates)—more attention must be given to understanding how these characteristics may also impact the recruitment and retention of program participants. The relationships between program characteristics and success at both the individual and the community levels should be examined. For example, it may be possible for a needle exchange program to be effective when limited to a small number of injection drug users, yet it may show no noticeable effect on either risk behaviors or HIV infection rates among the broader local population of injection drug users. By the same token, programs that reach larger populations may show a more modest effect among

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach participants, but also show that the effect extends into the broader community. Studies are needed to determine the relative effectiveness of programs that concentrate on intensively serving a limited client base versus those serving a broad population and providing fewer services. An issue related to the policy of setting limits on the number of syringes provided to individual participants per visit was raised earlier in this report. The potential effects of such program policies need to be further researched. Enforcing limits may discourage unintended consequences (e.g., individuals selling the needles they obtain); however, it could discourage participation because it may be inconvenient from the viewpoint of program participants (especially if participants have to travel a distance to reach the exchange). Specifically, research in this area should address questions such as: What are the relative benefits and risks associated with program policies related to the number of needles distributed? What are the potential benefits (e.g., broader diffusion of sterile equipment, reduced sharing) and harms (e.g., source of income for participants that may impact severity of drug addiction) that are related to other environmental and personal characteristics of program participants? Differential effectiveness of these programs across racial/ethnic, age, and gender populations must be further explored. Little is currently known about the relative effectiveness of these programs across population subgroups. In addition to research on the demographic characteristics, more research needs to be done to better understand how programs can have the most impact while taking into account the risk behaviors of program participants (i.e., drug use, sexual risks), both across and within programs. For example, the severity of drug addiction may be more pronounced in certain programs or within subsets of program participants, reflecting different risks that should be considered by program operations. Such research (e.g., development of needs assessment methods) could assist program operators in establishing the most effective combination of ancillary services particular to specific situations. The panel's review revealed that little is known about the effects of these programs on the level of illicit drug use in the community at large. Research indicates that the programs do not affect the level of drug use of their participants and do not appear to recruit new drug abusers to injection drug use. But results in this country necessarily relate to a relatively short time horizon. In principle, findings on a time scale of, say, a decade might be different. Here, then, are questions calling for research. Another unexplored area of research concerns the potential adverse effects these programs may have on certain risk behaviors of program participants (e.g., severity of drug use and sexually transmitted diseases). Do they inadvertently generate new social networks of drug users, which then may serve as a mechanism to facilitate viral spread, depending on the risk characteristics—drug

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach and sexual—of the new social network and the seroprevalence background level of infection of new groups? Similar concerns were raised when methadone maintenance treatment programs were first introduced. Understanding these interactions across social networks is crucial to developing a better perspective on the changing patterns of risks and the progression of the HIV epidemic. RESEARCH ON BLEACH EFFICACY IN DISINFECTION In addition to the issues listed above regarding needle exchange programs that are also relevant to evaluation studies of bleach distribution programs, there are others specific to bleach distribution programs. Although limited in some ways (see Chapter 6), laboratory studies have shown that bleach is an effective disinfection agent for HIV-contaminated materials. Yet current epidemiologic studies have revealed that bleach disinfection, as currently practiced by injection drug users, does not appear to have a protective effect. It is therefore crucial that educational methods be developed to improve the level of compliance by injection drug users with the recommended disinfection protocol. Laboratory studies are needed that carefully characterize the efficacy of bleach disinfection of needles and syringes under conditions that mimic field or actual use situations, accounting for bioburden and minimum effective contact times. These efforts should identify the optimal procedure while incorporating bioburden/consistency of use/contact time characteristics. Although some data are available, the panel noted limitations in current methods to assess efficacy (see Chapter 6). In terms of recommended field procedures, studies are needed to determine if injection drug users can perform, and under what circumstances are willing/or not to perform, the multistep procedures that are recommended (e.g., ethnographic research). If current procedures are too complex or unacceptable to injection drug users, then research is needed to identify safe and effective procedures that can be performed by them. Moreover, effective educational strategies are urgently needed. Information on the diffusion of education intervention effects over time and the possible benefit of booster sessions to ensure sustained beneficial effects needs to be further studied. In addition, effective modes of disseminating bleach information to injection drug users need to be further explored (e.g., relative effectiveness of media, outreach). EPIDEMIOLOGIC RESEARCH The HIV and AIDS epidemiologic data clearly document the critical role of injection drug use in the current and future course of the HIV epidemic

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach in this country. Our review of HIV infection rates among population subgroups of injection drug users (Chapter 1) indicates wide variation in geographic distribution of HIV infection. Likewise, there is considerable geographic diversity in patterns of injection drug use (e.g., drug used, frequency of injection) (see Chapter 2). The risk of transmission in a population depends on the reservoir of infection (as measured by HIV and other blood-borne pathogen seroprevalence) and the levels of risk behaviors that transmit infection. As these two parameters evolve, so does the epidemic. In order to minimize the occurrence of new infections, ongoing monitoring systems of HIV seroprevalence, seroincidence, and levels of risk behaviors can help guide interventions aimed at curbing new infections. The documented connection between injection drug use and AIDS points to the need to better understand the underlying dynamics of sexual/drug-use behaviors of high-risk groups, and how these networks are linked to other social networks within the intravenous drug user populations. Such an understanding could benefit from the development of theoretical research and alternative methodologies for studying such sensitive topic areas as drug-use and sexual behavior. To better achieve this goal, future research should include the following: Ongoing coordinated studies are needed of the seroprevalence and seroincidence of HIV, HBV (hepatitis B virus), and HCV (hepatitis C virus) among local populations of injection drug users, using standardized methodologies across locations. Extensive and repeated surveys of seropositivity rates are needed to determine the incidence and prevalence of infection by age, race/ethnicity, geographic area, and sex. Such studies should be performed locally with standardized protocols developed to ensure comparability of the collected data. Improved estimation procedures (including enhanced surveillance systems, modeling techniques, and ethnographic methods) should be developed for obtaining more accurate and time-relevant estimates of the number of drug users by city/county rather than attempting to obtain accurate national estimates. Detailed surveys that allow better characterization of specific drug-use behaviors and dynamics of drug-use patterns are needed. This will enable better-targeted prevention efforts. Developing a typology/demography of HIV infection that identifies high-risk groups in terms of prevalence and incidence and of risk behaviors is necessary to prevent the creation of potential epicenters. Attention should also be given to identifying subgroups or clusters within the broader defined risk groups—e.g., whether there are identificable groups at relatively different levels of risk within the population of local injection drug users. Delineating the characteristics of these subgroups of injection drug users

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach along such characteristics as the disparities in risk behaviors and/or patterns of risk behaviors would greatly assist targeting and tailoring prevention interventions. Regular, geographically detailed information about the prevalence of HIV (and, as useful surrogates, hepatitis B and C) could help guide priorities in mounting public health initiatives. Improved measurements of injection drug use and sexual risk behaviors are needed. Such measures should include information on: (1) patterns of drug use (e.g., drug type, route of administration, frequency of use, source of needles, patterns of reuse of needles); (2) direct and indirect sharing behavior; (3) patterns of sexual contacts (e.g., heterosexual, homosexual, frequency, number of patterns) and activities (e.g., receptive anal sex); (4) sexually transmitted diseases; and (5) drug and sexual social networks. Better understanding of certain biological and social parameters is needed, including the relative efficiency of different transmission routes, the kinetics, and the relative efficiency of known transmission routes (i.e., direct and indirect sharing). There is an urgent need to identify the key determinants of illicit drug injection at both the individual and the community levels. In particular, it is important to conduct etiologic studies of the transition from noninjection to injection drug use. Most individuals who inject illicit drugs begin this behavior in late adolescence or early adulthood (Gerstein and Green, 1993; Newcomb and Bentler, 1988; Chen and Kandel, 1995). Moreover, as mentioned in Chapter 2, a substantial number of those who reported having injected a drug in the past year were between the ages of 12 and 25. Chapter 3 also shows that needle exchange programs do not recruit a sizable number of young injectors. This highlights the need for recruiting study cohorts of younger individuals as part of ongoing efforts to further our understanding of injection drug use and improve AIDS prevention strategies. This is especially urgent because some studies have shown that seroconversion typically occurs during the early stages of injection drug use after initiation has occurred (Nicolosi et al., 1992; Moss et al., 1994; Nelson et al., in press). RESEARCH ON COMMUNITY ISSUES Chapter 4 of this report highlighted the severity of the drug abuse problem in our society. Injection drug use ruins the lives of users and of those close to them. HIV and AIDS have only worsened the situation. Coping with these public health problems is much more likely to succeed if we fully understand them. Moreover, critical to the effective implementation of HIV

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach and AIDS preventive interventions is a better understanding of local community concerns. More systematic research is needed on other ethnic groups who are known to be at high risk of infection (e.g., Puerto Ricans in New York City). This panel recognized its own limitations in attempting to address the issues and concerns of the multitude of communities that are summarized simply as Hispanic/Latino. More detailed investigation and response are needed. Although some pharmacists, law enforcement officers, and treatment service providers have been supportive of needle exchange programs, others have expressed concerns and reservations about their potential role in making sterile injection equipment more readily available to injection drug users. A better understanding of the beliefs, attitudes, values, and motivational factors that influence these reservations needs to be developed through both qualitative and quantitative research efforts. OTHER FUTURE RESEARCH ISSUES Deregulation of Syringe Sale and Possession Within the context of deregulation of pharmacy sales and possession of needles, important issues warrant further research. For example, the practice of sharing needles and syringes continues in industrialized countries other than the United States. Some of these countries have needle exchange programs and no paraphernalia or prescription laws limiting the availability of sterile injection equipment. These circumstances lead the panel to suggest that: Researchers need to identify the causal agents involved in sharing after legal constraints are removed. Ethnographic research should identify why needles and syringes continue to be shared when community availability is no longer a constraint (see Chapter 5, time of injection versus community availability issues). In terms of the deregulation of syringe sale and possession (allowing injection drug users to purchase syringes in pharmacies), one important concern that requires immediate attention is that of developing efficient disposal methods for used needles and syringes. Pharmacies, with numerous locations and hours of operation, are convenient and accessible for obtaining syringes. However, the issue of appropriate needle and syringe disposal needs further consideration and planning.

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach Incarcerated Populations Members of highly vulnerable populations, such as injection drug users, are known to frequently come in contact with various social institutions. These include public medical facilities, such as drug treatment facilities, clinics for treating sexually transmitted diseases, emergency rooms, and correction facilities. For example, more injection drug users can be found in prisons than in drug treatment programs, hospitals, and social services (Brewer and Derrickson, 1992). It is plausible that preimprisonment drug-use behavior among incarcerated injection drug users will be more heterogeneous than that of users in treatment facilities or needle exchange programs (Vlahov and Polk, 1988). Moreover, Siegal et al. (1994), in a study that examined the relationship between level of HIV risk behavior and history of exposure to jail or prison, report that active injection drug users with the highest HIV risk behaviors were those most likely to spend time in jail. These findings, combined with the fact that more than 4 million people are incarcerated annually in the United States, argue for devoting more prevention research efforts to this subpopulation of injection drug users. Randomized Trial of Needle Exchange Programs The emphasis of this chapter has been on identifying research issues that need to be vigorously pursued in order to improve the current knowledge base. In addition, we feel that the issue of randomized trials of needle exchange programs should be addressed, because some researchers have argued for their implementation to adequately answer issues concerning the effectiveness of such programs. As was stressed in a previous National Research Council evaluation report on AIDS (Coyle et al., 1991), the randomized experiment might be the ideal scheme to adopt when attempting to assess the effect of AIDS prevention strategies. That report acknowledged, however, that because of practical constraints (e.g., complying with true random assignments of individuals or communities, inability to provide ''blinding" of behavioral interventions, treatment attrition, cost), one may choose to focus instead on well-conceived observational epidemiologic designs. These practical constraints are severe in the case of needle exchange and bleach distribution programs. The more important problems associated with randomized trials (i.e., randomized field experiments) are practical. There are currently over 55 cities in the United States that have implemented needle exchange programs. This places serious constraints on finding comparable communities that do not have needle exchange programs and would be willing to be

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach randomized. Moreover, given the sensitive nature of these programs (in contrast with smoking cessation programs, for example), many volunteer communities may not be capable of initiating proper legislative change (of paraphernalia and prescription laws) to legally allow such programs to take place. Furthermore, given the results of the two recent government-sponsored reports that have concluded that these programs have positive effects and do not appear to have negative impacts (U.S. General Accounting Office, 1993; Lurie et al., 1993), it may not be ethical to withhold treatment from communities willing to initiate such programs. Problems may also arise because communities eager to participate may proceed with program implementation after having been informed that they have been assigned to the control condition. In addition, one major concern with these designs in prevention research is differential attrition rates across conditions. As Booth and Watters (1994) point out in their review of risk reduction interventions, participation in the treatment condition is more demanding than in the control condition, which typically leads to experimental attrition. Cost is a factor, particularly when treatments are randomized across large units, such as cities or communities, rather than across individuals. Only a small number of units may be assigned to conditions. Yet the strength of randomization depends on the random assignment of a sufficiently large number of units to substantially weaken the possibility that confounding factors would coincidentally vary with the random assignment. When only a small number of units are randomly assigned to conditions, given the low probability that the treatment and control conditions will be equivalent on unmeasured factors, sensitivity is necessarily reduced. The panel recommends adopting strong observational epidemiologic designs (i.e., prospective and case-control studies) rather than attempting to conduct large-scale randomized experiments to evaluate needle exchange and bleach distribution programs. BROADER ISSUES To better understand the workings of needle exchange and bleach distribution programs and how to render them more effective, we need a deeper understanding of many phenomena that are not specific to needle exchange and bleach distribution programs but are more general in scope. For example, we need to know about the processes of addiction, about the propagation of infectious diseases, about the dynamics of social networks, about the underlying factors in personal failure and success, and about the role of sexual behaviors in the lives of injection drug users.

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach Motivation and attitude are central to behaviors that are implicated in the spread of HIV infection: intravenous drug use and unprotected sex. It would be particularly valuable to explore how the underlying attitudes and motivations can be modified. Social networks, especially among injection drug users, appear to exert large effects on recruitment to, and attrition from, needle exchange and bleach distribution programs. They are also implicated in needle-sharing behavior. Research in this area would contribute to better understanding of how social networks affect program participation (and nonparticipation). CONCLUSION The HIV epidemic in the United States is growing largely because of infection spread by contaminated needles in the population of injection drug users. Needle exchange and bleach distribution programs can help to retard this spread. And, to the extent that these programs can be made to be more effective, their retardant effect will be greater. To improve the effectiveness of needle exchange and bleach distribution programs calls for additional research, including arrangements for collecting findings across sites and coordinating studies at various locations. Good, up-to-date local measures of seroprevalence, not only of HIV but also of HBV and HCV, would help greatly to target program efforts and resources. Finally, to make a difference, resources must flow to these research tasks. An infusion of funds, personnel, and training would all yield important returns. To live now with this epidemic without knowledgeably combatting it would be shortsighted. In the long-term control of HIV and AIDS, the kinds of research we propose would be thoroughly worthwhile. REFERENCES Booth, R.E., and J.K. Watters 1994 How effective are risk-reduction interventions targeting injecting drug users? [editorial]. AIDS 8(11):1515-1524. Brewer, T.F., and J. Derrickson 1992 AIDS in prison: A review of epidemiology and preventive policy [editorial]. AIDS 6(7):623-628. Chen, K., and D.B. Kandel 1995 The natural history of drug use from adolescence to the mid-thirties in a general population sample [comment]. American Journal of Public Health 85(1):41-47. Coyle, S.L., R.F. Boruch, and C.F. Turner, eds. 1991 Evaluating AIDS Prevention Programs: Expanded Edition. Panel on the Evaluation of AIDS Interventions. Washington, DC: National Academy Press. Gerstein, D.R., and L.W. Green, eds. 1993 Preventing Drug Abuse: What Do We Know? Committee on Drug Abuse Prevention

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Preventing HIV Transmission: The Role of Sterile Needles and Bleach Research, National Research Council. Washington, DC: National Academy Press. Gerstein, D.R., and H.J. Harwood, eds. 1992 Treating Drug Problems: Volume 1. Committee for the Substance Abuse Coverage Study. Washington, DC: National Academy Press. Gleghorn, A., T.S. Jones, M. Doherty, D. Celentano, and D. Vlahov in press Acquisition and use of needles and syringes by injecting drug users in Baltimore, Maryland. Journal of Acquired Immune Deficiency Syndromes. Lurie, P., A.L. Reingold, B. Bowser, D. Chen, J. Foley, J. Guydish, J.G. Kahn, S. Land, and J. Sorensen 1993 The Public Health Impact of Needle Exchange Programs in the United States and Abroad, Vol. 1. San Francisco, CA: University of California. Moss, A.R., K. Vranizan, R. Gorter, et al. 1994 HIV seroconversion in intravenous drug users in San Francisco, 1985-1990. AIDS 1994 8:223-231. Nelson, K.E., D. Vlahov, L. Solomon, S. Cohn, and A. Muñoz in press Temporal trends of incident HIV infection in a cohort of injection drug users in Baltimore, Maryland. Annals of Internal Medicine. Newcomb, M.D., and P.M. Bentler 1988 Impact of adolescent drug use and social support on problems of young adults: A longitudinal study. Journal of Abnormal Psychology 97(1):64-75. Nicolosi, A., M.L.C. Leite, S. Molinari, et al. 1992 Incidence and prevalence trends of HIV infection in intravenous drug users attending treatment centers in Milan and Northern Italy, 1986-1990. Journal of Acquired Immune Deficiency Syndromes 5:365-373. Siegal, H.A., M.A. Forney, R.G. Carlson, and D.C. McBride 1994 Incarceration and HIV risk behaviors among injection drug users: A Midwestern study. Journal of Crime and Justice XVI(1):85-101. Stimson, G.V., L.J. Aldritt, K.A. Dolan, M.S. Donoghoe, and R.A. Lart 1988 Injecting Equipment Exchange Schemes. Final Report. London: Monitoring Research Group, Goldsmith's College. U.S. General Accounting Office 1993 Needle Exchange Programs: Research Suggests Promise as an AIDS Prevention Strategy. Washington, DC: U.S. Government Printing Office. Vlahov, D., and R.S. Brookmeyer 1994 The evaluation of needle exchange programs [editorial]. American Journal of Public Health 84(12):1889-1891. Vlahov, D., and B.F. Polk 1988 Intravenous drug users and human immunodeficiency virus infection in prison. AIDS Public Policy Journal 3:42-46.

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