1 Baron Edmond de Rothschild Chemical Dependency Institute, Beth Israel Medical Center, New York, NY.
2 National Development and Research Institutes, Center for AIDS Research, New York, NY.
3 New York Academy of Medicine, Center for Urban Epidemiologic Studies, New York, NY.
4 ThailandUnited States Collaboration, Centers for Disease Control and Prevention, Atlanta, GA.
Received for publication July 17, 2001; accepted for publication September 24, 2002.
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ABSTRACT |
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cohort studies; hepatitis B virus; hepatitis C-like viruses; HIV; injections, intravenous; substance-related disorders
Abbreviations: Abbreviations: HBV, hepatitis B virus; HCV, hepatitis C virus; HIV, human immunodeficiency virus.
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INTRODUCTION |
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There are also important differences with respect to the transmission dynamics of these three viruses in populations of injecting drug users. HBV and HCV are more environmentally stable and more readily transmitted than HIV (6). The prevalence of persons chronically infected with HCV is often much higher than the prevalence of persons infected with HIV in populations of injecting drug users. Incidence rates are also typically much higher for HBV and HCV infection than for HIV infection. The incidence of HCV infection can be extremely high among persons who have recently begun injecting drugs, with estimated rates of from 32 to more than 70 per 100 person-years at risk (7, 8).
We report here on the incidence of HIV, HBV, and HCV infection in two cohorts of young drug injectors from New York City, New York. We found substantial variability in incidence, both among the viruses and across the two study sites.
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MATERIALS AND METHODS |
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Eligibility
Study participants were persons between the ages of 18 and 30 years who reported injecting drugs during the previous 6 months. Questions to assess eligibility were asked within a series of unrelated questions (e.g., Do you have siblings?). The eligibility criteria were not advertised, because knowledge of these criteria might have led persons to falsely represent themselves in order to enter the study.
Sites
The Harlem study, known as Harlem Outreach Prevention and Education (HOPE), was conducted from a building in central Harlem. Recruitment took place in both central (predominantly African American) and east (predominantly Latino/Latina) Harlem.
For the Lower East Side, the study was conducted in a research storefront office in that neighborhood. The storefront has been in continuous operation since 1989 and is well known among drug users in the community. The Lower East Side is an ethnically diverse neighborhood with a large transient population of young White persons from the rest of the United States.
Recruitment procedures
Ethnographic interviews, health and law enforcement statistics, and direct observation were used to map central and east Harlem and the Lower East Side to determine specific areas in which young drug injectors congregated. Recruiters then approached young persons in these areas, engaged them in conversation, and formally assessed eligibility by asking structured questions, inviting those who were eligible to participate in the study. Persons who agreed to participate were escorted to the study office to receive information about the study and to provide informed consent. After completing an interview, they were given a small honorarium ($25) for their time and travel.
Data collection
At baseline and at 6 and 12 months postbaseline, eligible and consenting participants underwent standardized face-to-face interviews conducted by trained interviewers in private rooms. Participants received pretest counseling for HIV, HBV, and HCV infection, and serum samples were collected. After data collection, participants were given risk-reduction counseling and referral information for services such as drug treatment and social services. At post-test counseling (approximately 24 weeks after the interviews), participants whose test results were positive were offered referrals for follow-up medical evaluation. Those without evidence of HBV infection were offered referral for hepatitis B vaccination.
The study received institutional review board approval from Beth Israel Medical Center, the National Development and Research Institutes, the New York City Department of Health, and the Centers for Disease Control and Prevention.
Interviews
The interview included questions on sociodemographics, injecting behaviors, risk networks, and sexual behaviors. Most drug use and sexual behavior questions focused on the 6 months prior to the baseline interview, and then on the periods between successive interviews.
Laboratory analyses
Serum from blood specimens was analyzed for HIV-1 antibodies by using standard techniques at local laboratories. Specimens repeatedly reactive on enzyme-linked immunosorbent assay were confirmed with Western blot.
Blood specimens were sent to the Centers for Disease Control and Prevention for testing for serologic markers of HBV and HCV infection. Samples were tested for antibody to HBV core antigen (CORAB; Abbott Laboratories, Chicago, Illinois) and antibody to HCV (Abbott HCV EIA (enzyme immunoassay) 2.0; Abbott Laboratories). A sample of 100 specimens repeatedly reactive for HCV based on enzyme immunoassay received supplemental testing (EIA 2.0 and HCV MATRIX; Abbott Laboratories); all were found to be positive. Because of the high positive predictive value of repeat reactive enzyme immunoassay testing in this population, no further supplemental HCV testing was performed. Seroconversion was defined as a negative anti-HIV, anti-HCV, or antibody to HBV core antigen test at one data collection point followed by a corresponding positive anti-HIV, anti-HCV, or antibody to HBV core antigen test at the next data collection point. Time of seroconversion was estimated as the midpoint between the dates of serum collection of the last negative antibody test and the first positive antibody test.
Follow-up procedures
Follow-up visits were scheduled for 6 and 12 months after the baseline visit. Standard follow-up procedures were conducted at each site, including collecting detailed locator and contact information; maintaining telephone, mail, or in-person street contact with subjects; and providing honoraria for participation in follow-up interviews, with bonus incentives for subject-initiated appointments. For subjects who did not provide usable contact telephone numbers or addresses, recruiters conducted street searches of initial recruitment locations and typical "hangout" locations.
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RESULTS |
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We examined possible differences in baseline variables (those listed in table 1) between subjects for whom follow-up data were or were not available. In general, very few differences were found in baseline risk behaviors between subjects who were or were not followed up successfully. In particular, there were very few differences for the Lower East Side site, which had the lower follow-up rate (data not presented but are available from the first author).
Table 2 presents the incidence rates for HIV, HBV, and HCV infection for the two sites and for the combined sample. HIV incidence was similar at both sites and was low for areas in which HIV seroprevalence was high (approximately 30 percent among injecting drug users as a whole at each site (9) at the time of the study). At the Harlem site, the incidence of both HBV and HCV infection was approximately 10 per 100 person-years at risk, and the incidence of both HBV and HCV infection was approximately 30 per 100 person-years at risk at the Lower East Side site.
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DISCUSSION |
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The incidence of HIV among these young injecting drug users at both sites is consistent with that found in other recent HIV incidence studies from New York City. A meta-analysis of 12 studies that included 6,000 person-years at risk found a weighted average incidence of 0.7 per 100 person-years at risk (10)similar to the incidence rates of 0 per 100 person-years and 0.8 per 100 person-years found in the two samples of young injectors in this study. Indeed, given the other recent HIV incidence studies (10) among injecting drug users in New York, a high HIV incidence rate at either site would be unexpected and would require special explanation.
Low HIV incidence and moderate-to-high HCV/HBV incidence has been reported in studies from other areas, for example, those by van Beek et al. and Hagen et al. (8, 12). To the best of our knowledge, however, these other studies showing a low HIV and a high HCV/HBV incidence among injecting drug users were conducted in geographic areas in which the HIV prevalence was very low. The low prevalence of HIV may be a sufficient explanation for the differences in HIV versus HBV/HCV incidence in these other areas. However, this explanation would not apply to the New York City data reported here, because HIV prevalence in both the Harlem and Lower East Side areas was approximately 30 percent when the data were collected (10).
These follow-up samples can be considered convenience subsamples of the original convenience samples from the cohorts. Thus, these incidence rates should not be generalized to other young drug injectors in New York City, nor necessarily even to other young drug injectors from the two neighborhoods. However, our results do demonstrate that considerable variability can occur in the incidence rates of the three viruses in different groups of injecting drug users.
These data raise the question of how so many of the follow-up subjects became infected with HBV and HCV without becoming infected with HIV. As shown in table 2, among the follow-up subjects, there were 32 incident HBV infections and 25 incident HCV infections but only one incident HIV infection. We suggest two possible mechanisms for the differences between HBV and HCV versus HIV incidence. First, recent studies suggest that HBV and/or HCV frequently may be transmitted by sharing drug preparation equipment (cottons, cookers, rinse water) (11, 12), while it does not appear that HIV is often transmitted by sharing such drug preparation equipment. In the baseline data for this study, prevalent HCV infection was associated with the sharing of drug preparation equipment (13). Thus, HBV and HCV but not HIV may have been transmitted because young drug injectors in New York shared drug preparation equipment.
Second, the great majority of injecting drug users in New York have been tested for HIV, and injecting drug users who know that they are HIV seropositive are much less likely to pass on used needles and syringes compared with injecting drug users who know that they are HIV seronegative (Des Jarlais et al., unpublished manuscript). We doubt whether most injecting drug users in New York know 1) whether they are infected with and are capable of transmitting HBV and/or HCV infection and 2) the possible outcomes of chronic HBV and HCV infection; and whether those who know that they are capable of transmitting HBV and HCV are substantially reducing their transmission behaviors (passing on used needles and syringes).
There are two implications of the variability in the incidence of HIV, HBV, and HCV in these two groups of new drug injectors in New York. First, great caution is needed before either HBV incidence or HCV incidence is used as an outcome measure to assess HIV prevention programs. High HBV or high HCV incidence need not imply high HIV incidence and may not even imply a potential for high HIV incidence (although we think that low HBV/HCV incidence probably does imply low HIV incidence).
Second, it is likely that new methods of preventing HBV and HCV transmission among injecting drug users are needed. Vaccinating drug users against HBV is likely to be the most effective way to prevent HBV infection, but, at present, efforts to vaccinate drug users for HBV in the United States and many other countries are clearly inadequate. Reducing HCV transmission may be quite difficult. It is likely that further reductions in the sharing of both needles and syringes and of drug preparation equipment will be needed. We suggest that new efforts to reduce HCV transmission among injecting drug users should be developed in consultation with the injecting drug users themselves.
Reducing HIV, HBV, and HCV transmission among injecting drug users is an important public health goal. Clearly, additional research is needed on the transmission dynamics of HIV, HBV, and HCV in this population. Although there are broad similarities in how these three viruses are transmitted, important differences in the design and evaluation of programs may be needed to achieve this goal.
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NOTES |
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REFERENCES |
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