The effectiveness and limitations of syringe exchange programmes throughout the world
Julien Emmanuelli
Physician and author of Caractéristique et efficacité des programmes d'échanges de seringues à travers le monde: états des lieux et perspectives, 1999 Institut de veille sanitaire,

Syringe exchange measures are among the main emergency measures which can be applied in situations where injecting drug users are being contaminated with the HIV virus. The scientific literature published all over the world has confirmed that these measures are effective, but only under specific conditions.

Some countries have had to cope with thousands of infections because they responded to the challenge too slowly.

Although we have no definite epidemiological proof that syringe exchange programmes are effective, since it is impossible to perform experimental studies here, as in many other public healthcare situations, there is a growing body of evidence that syringe exchange programmes (SEPs)* generally lead to a decrease in the spread of HIV without increasing the consumption of drugs, the injection rates, the number of injecters or the number of used syringes left lying in the streets. Attending an SEP also tends to lead to a decrease in drugrelated, as opposed to sex-related, risk behaviour. Some countries; such as Britain, Australia and the Netherlands, have therefore no doubt managed to prevent the occurrence of an HIV epidemic amongst their injecting drug users (IDUs) by introducing SEPs at an early stage, along with other public health measures, while other countries have fared much less well, and have had to cope with thousands of infections because they reacted too slowly (as in the case of France) or too late and without any political support (as in that of the United States and Brazil).

However, the positive effects of SEPs must not blind us to their limitations. For instance, SEPs are probably much less effective means of controlling the spread of the hepatitis C and hepatitis B viruses. This is one of the findings which has emerged from the study on the RAVEN (1) cohort, a group of 1238 intravenous drug users with low rates of HIV and hepatitis B infection (0.2% and 5%, respectively) and a surprisingly high rate of hepatitis C infection. The fact that the classical harm reduction measures are not ver effective methods of combating hepatitis C virus is no doubt due to the high prevalence* of this virus, the existence of as yet unexplored paths of transmission (the sharing of injecting paraphernalia other than syringes, for instance) and to the likelihood that this virus may be more resistant to bleach. In addition, SEPs do not operate in a vacuum, and their biological and behavioural effects no doubt depend on a combination of environmental factors.

Among the reasons why SEPs have failed to prevent HIV infection, some authors have mentioned the fact that a lack of availability of syringes can have an impact on the effectiveness of these programmes. This was possibly the case, according to Lurie (2), in Montreal in 1994, where the number of syringes distributed by the SEP was woefully insufficient, as was also probably true in Vancouver, where even the two million syringes distributed annually by the SEP were probably did not match the demand for syringes resulting from the upsurge in the use of cocaine, which was being injected anything between 5 and 10 times a day on average when taken intravenously.

In their international review (3), Stadhee et al. speak of "social marketing" to illustrate

the need for SEP directors to accurately predict the number of injections liable to occur and to reach or sensitise all the sub-populations involved (prisoners and IDUs belonging to various social, racial and ethnic minority groups). This is all the more crucial in areas where there is a high prevalence* of HIV, as even low rates of needle sharing can lead to high levels of infection (and this is certainly doubt truer still of the hepatitis C virus).

IN THIS CONTEXT, YOUNG USERS AND NEW INJECTORS are causing great concern to the authors because of the often high levels of HIV (as well as hepatitis C) occurring among these groups (4), where it is difficult to change attitudes and practices. People in the younger age- groups do not encounter the problems which make older users consult or contact harm reduction structures, and in addition, do not even think of themselves as drug addicts of feel that the harm reduction messages circulating have anything to do with them.

APART FROM MATCHING THE SUPPLY OF SYRINGES TO THE DEMAND, SEP action cannot effectively prevent the occurrence of some particularly high-risk scenarios. According to Moss and Hahn (5), whenever an HIV epidemic reaches a peak among the IDUs (as occurred in Vancouver), SEPs do not seem to constitute a very useful response in the short term, probably because lack of access to sterile injection paraphernalia is not the only reason for syringe sharing. Several authors have described how some dealers who are rather unscrupulous about their customers' health propose ready prepared syringes containing a dose of drugs (6). A somewhat less cynical cause is the sharing out of a batch of drugs in such a way that the drug comes into contact with contaminated syringes, cups, and even the water used to dilute the drugs becomes indirect an indirect source of HIV transmission (and hepatitis C) not associated with needle sharing per se (7). And rarely, but certainly very dangerously, the blood of one IDU at an injecting session is sometimes diluted and used in cooking up a "kitchen sink" opiate solution (8).

AS REGARDS THE ENVIRONMENTAL FACTORS which may contribute to reducing or even abolishing the effectiveness of SEPs on the incidence of HIV, a few writers have underlined the importance of the location of the project, which may be affected by the proximity of a red light area or the absence of a local alternative to the SEP (pharmacies or distributors, for example).

Other authors, in greater numbers, have emphasised the high-risk profile of the IDUs attending SEP's, and have sometimes taken this feature to be a sign of success (in that they attract people whose lifestyle and behaviour mean that they should be given priority access to the syringes they cannot in some cases obtain elsewhere), and sometimes a source of increased risk.

ALL-ROUND ANALYSES OF THE FACTORS AND CONDITIONS LIMITING the effectiveness of these programmes have pointed to the conclusion that although they may help to prevent HIV, SEPs can only work in a given situation as a possible alternative to other risk reduction strategies based on more community-oriented interventions (peer groups* informing other young IDUs and increasing their awareness, for example).

IN CONCLUSION, AMONG THE COMPLEMENTARY ACTIONS REQUIRED In addition to SEPs as they stand, Stadhee et al (3) have stressed the need to prevent injecting practices themselves as far as possible. These authors mention how little scientific attention has focussed on this point (9), I an point out that injecting practices expose their practitioners to a significantly higher risk of morbidity* and mortality from overdose, endocarditis, septicaemia and abscesses, apart from the risk of viral infection. They argue that the efforts made on SEP lines have been undermined by the lack of available treatments for drug addiction and by the lack of available cocaine substitutes. Tackling the practice of injection involves studying the underlying causes of intravenous drug use and then combating these processes preventively via actions aimed at community rather than individual level. It has been said (3) for example that a lower level of availability or purity of a product may lead users either to take to injecting (as in the closely related case of the crack explosion occurring in the USA: crack constitutes a more economic alternative to powdered cocaine) or to switch to another injectable product (as with injectable buprenorphine in India: this medicinal product is now being misused by many IDUs who are no longer able to procure heroin).

1 Incidence of blood-born viruses in a cohort of Seattle IDUs, H.Hagan, Department of Public Health, Seattle,USA, Xlth International conference on AIDS/HIV, Vancouver, 7-12 July 1996.

2 lnvited commentary: the mystery of Montreal, P.Luric, American Journal of Epidemiology, Vol. 146 No l2, 1003-1006, 1997.

3 Measuring harm reduction: the effect of needle and syringe exchange programs and methadone maintenance on the ecology of HIV, E.Drucker, P.Lurie, A.Wodak and P.Alcabes, AIDS, 1998,12, suppl. A:S217-S320.

4 High rates of HIV infections among IDU's participating in needle exchanges in Montreal: result ofa cohort study, j.Bruneau, F.Lamothe, F.Franco et. al, American Journal of Epidemiology,1997, 146:9941002.

5 Invited commentary: Needle Exchange-No help for hepatitis, American Journal of Epidemiology, vol.l49, No3, 1999, 214-216, A.R.Moss and J.A.Hahn.

6 Rising HIV infestion in Ho-Chi-Minh city herald emerging AIDS epidemic in Vietnam, AIDS, 1997, 11(suppl)/ S-5-S-13, Uindan,T.Licu, IT Giang ct al.

7 CDC, IIRSA, NIDA, SAMSHA: HIV Prevention Bulletin : Medical advice for persons who injected illicit Drugs, Baltimore, US Dept of Health and Human services, 1997.

8 The first Moscow exchange program, Galybin et al, Vllth International Conference on the reduction of drug related harm, Paris 1997. 9-Maximum impact of HIV prevention measures targeted at injected at injecting drug users, van Ameijden EJ, Cominho RA, AIDS 1998 Apr 16; 12(6) : 625-33.