Sign the Resolution
Contents | Feedback | Search
DRCNet Home | Join DRCNet
DRCNet Library | Schaffer Library |Miscellaneous

Findings On average, seroprevalence increased by 5·9% per year in the 52 cities without NEPs, and decreased by 5·8% per year in the 29 cities with NEPs. The average annual change in seroprevalence was 11% lower in cities with NEPs (95% Cl -17·6 to -3·9, p=0·004).

The HIV epidemic in injecting drug users has reached crisis proportions, moving from its original focal points in Europe and North America to major outbreaks in Asian cities. ¹ In the USA alone, use of injection-drugs was the direct or indirect cause of almost 26 000 cases of AIDS in 1995, comprising 35% of all new cases. ² Needle-exchange programmes (NEPs) are potentially a key strategy for containing this epidemic, but they are not universally accepted. Government-funded NEPs are well established in several countries, including the UK, the Netherlands, and Australia. ³ However, there is still strong opposition to their implementation in the USA, where federal funding of NEPs has been prohibited until "the Surgeon General determines that such programs are effective in preventing the spread of HIV and do not encourage the use of illegal drugs". ^{4 !} State prescription and paraphernalia laws, which restrict the possession and distribution of needles and syringes, are a further impediment to the operation of NEPs in the USA. ⁵ Although NEPs had been established in 55 US cities by 1994, ⁴ many operate illegally, with tenuous funding, and on a small scale. ^4,5

Several observational studies have attempted to assess the effectiveness of NEPs in preventing HIV transmission. Most of these studies relied on surrogate endpoints such as self-reported risk behaviours, ^4,5 or the occurrence of infections with hepatitis B or C virus. ⁶ The few studies that used HIV endpoints either compared HIV seroincidence rates or HIV seroprevalence in small numbers of NEP participants and non-partcipants, or correlated time trends in HIV seroprevalence for a single city with the introduction of NEPs. ^4,7 Three reviews of NEP effectiveness commissioned by the US federal government since 1993 ^4,5,8 found that the evidence in favour of the effectiveness of NEPs was weak by accepted scientific standards. The goal of our study was to examine the effectiveness of NEPs with an approach that overcame so! me of the methodological limitations of previous studies. We used an ecological study design to compare changes over time in HIV seroprevalence in injecting drug users worldwide, for cities with and without NEPs.

Methods

Our analysis compared cities that had NEPs with those that had no NEPs. Programmes that distributed needles and syringes free of charge were regarded as NEPs, irrespective of how they operated (ie, from a fixed or mobile site, whether return of a used needle was mandatory, or the range of additional preventive services offered). We identified published reports of HIV seroprevalence surveys in injecting drug users that included 50 or more drug users and details of the implementation of NEPs in the corresponding city were obtained from reports and through communication with public-health officials and NEP researchers. We searched entries on Medline from between 1984 and May, 1994, HIV seroprevalence studies of injecting drug users and implementation of NEPs. Unpublished information on HIV seroprevalence was obtained from the Centers for Disease

____________________________________________ 

Correspondence to: Dr Susan F Hurley, Research and Development Division, CSL Limited, 45 Poplar Rd, Parkville, Victoria 3052, Australia (e-mail: shurley@csi.com.au)

____________________________________________ 

About 3500 published papers were reviewed, and information that satisfied the inclusion criteria for the study was obtained from 214 of these (references available from the authors on request). A total of 81 cities with HIV seroprevalence measurements from more than 1 year and information on NEP implementation were identified. 54% of these cities were in North America, 32% in Europe, and 12·4% in Asia and the South Pacific (table 1). In these cities, 1046 surveys of HIV prevalence involving 332892 drug users had been done between 1980 and 1993, 75% in drug treatment centres (table 1). Some serum specimens had been collected and stored, and were analysed when HIV tests became available. There were NEPs during the seroprevalence period in 29 (36%) cities; the mean duration of NEP implementation was 3·8 years (range 1-8). Seroprevalence was slightly higher at! the start of the seroprevalence period in cities without NEPs than in cities with NEPs, and by the end of the seroprevalence periods average HIV seroprevalence had changed little in cities with NEPs, but had increased in cities without NEPs (table 1).

NEPs were not operating during the seroprevalence period, the rate of change of the log odds of seroprevalence was estimated to be 0·677 per year (SE 0·123), corresponding to a 96·8% increase each year (95% CI 53·8-150·0). In Glasgow, UK, NEPs were introduced in 1987. The estimated rate of change in the log odds of seroprevalence was -0·286 (0·042), corresponding to a 24·9% annual decrease in seroprevalence (-18·3 t! o -30·9).

Seroprevalence was estimated to have increased in 58% of cities without NEPs and 48% of cities with NEPs (table 2). The regression model showed that seroprevalence increased on average by 5·9% per year in the 52 cities without NEPs, and decreased by 5·8% per year in the 29 cities with NEPs--- a difference of 11% (-17·6 to -3·9, p=0·004). The number of needles distributed over the seroprevalence period per 1000 injecting drug users was known for 21 cities, but was not a significant predictor of the rate of change of seroprevalence.

When analysis was restricted to cities with seroprevalence periods of more than 3 years with an initial seroprevalence below 10% we found that, on average, seroprevalence decreased by 1%, in the eight cities with NEPs compared with a 16% increase in the 18 cities without NEPs (figure 2), but this difference (-14·8 [95% CI -34 to 10]) was not significant. However, the regression modelling gave estimates of more than 10% for seroprevalence at the start of the period for four cities without NEPs, and one city with NEPs, apparently because the earliest surveys included fewer drug users and were consequently given less weight in estimation of slopes. Any bias would have caused the effectiveness of NEPs to be underestimated.

NEPs have the potential to decrease directly HIV transmission by lowering the rate of needle sharing ¹¹ and the prevalence of HIV in needles available for reuse, ¹² as well as indirectly through activities such as bleach distribution, referrals to drug treatment centres, provision of condoms., and education about risk behaviour. Although these mechanisms have strong theoretical support, the published evidence for NEP effectiveness is limited. Previous studies of the effect of NEPs on HIV incidence used observational designs or statistical models.

Observational designs included case studies; crosssectional, serial cross-sectional, and cohort studies (often without comparison groups); and case-control studies. ^4,5 Only one study assessed the impact of NEPs on HIV incidence. Des Jarlais and colleagues 7 estimated that the hazard for incident HIV infection was 3·3 for injecting drug users in four high-seroprevalence cities without NEPs, compared with continuous users of NEPs in New York City. One case study investigated HIV prevention activities for five cities with low seroprevalence, but did not formally compare these with other cities that had high seroprevalence. ¹³ The most frequently cited statistical model for assessment of NEP effectiveness was developed by the New Haven NEP evaluators, and is based on the theory that NEPs decrease HIV transmission rates by lowering the time that needles are in circulation. ¹⁴