Sixteen years after needle/syringe programs (NSPs) were first introduced in Australia, after a period of civil disobedience and amid intense controversy, the recent report Return on investment in needle and syringe programs in Australia1 has convincingly confirmed the effectiveness of NSPs in reducing HIV and hepatitis C virus (HCV) infection among injecting drug users. The report also draws attention to the program's low cost and high cost-effectiveness.

Commissioned by the Commonwealth Department of Health and Ageing, the report summarises 778 years of data from 103 cities around the world. In cities that had ever had NSPs, there had been an average annual decrease in HIV prevalence of 18.6%, compared with an average annual increase of 8.1% in cities without such programs.

Australia's NSPs were estimated to have cost Commonwealth and State governments $122 million by 2000, but the return on this investment was the prevention of an estimated 25 000 HIV and 21 000 HCV infections. By 2010, our NSPs will have prevented an estimated 4500 deaths from AIDS and 90 deaths from HCV. The savings to governments for HIV and HCV were estimated to be at least $2.4 billion (allowing for conventional government 5% annual discounting of future costs) or as much as $7.7 billion (without discounting). By any reckoning, this represents an enormous saving in both lives and dollars. In light of these outcomes, opposition to NSPs amounts to public health vandalism and financial recklessness with taxpayers' dollars.

However, in spite of these gratifying health outcomes for investments in NSPs, the annual incidence of HCV in Australia continues to rise.

Hepatitis C is a very common chronic infection in Australia. At least 80% of infected people have acquired HCV through injecting drug use. A recent report2 estimated that in Australia in 2001 there were about 210 000 people with HCV antibodies, of whom 53 000 had cleared their HCV infection, 151 000 were living with chronic HCV infection and 6500 were living with HCV cirrhosis.

Furthermore, according to the report, despite the effectiveness of NSPs in reducing HCV incidence among injecting drug users (IDUs), there were 16 000 people exposed to HCV during 2001, representing a 45% increase on the estimated 11 000 incident HCV infections in 1997.3 The report also projected that the long-term sequelae of HCV infection, such as cirrhosis, liver failure and hepatocellular carcinoma, would all treble by 2020.

These two reports1,2 raise several important questions. First, why have NSPs been so successful at limiting HIV infection among IDUs, but less effective in reducing HCV infection? One important reason for the apparent discrepancy is the greater infectiousness of HCV by blood–blood spread compared with HIV, and consequently its heightened transmission among IDUs. Another factor is the higher baseline HCV levels (of the order of 50%–70%) prevalent among IDUs when NSPs were introduced in Australia in the late 1980s.4 At that time, only one in 200 IDUs undergoing treatment in Sydney were infected with HIV.5 HIV appears to have entered IDU populations in Australia in the early 1980s, about 20 years after HCV.6

Second, why has HCV incidence continued to increase so rapidly in Australia throughout the 1980s and 1990s, despite early and vigorous implementation of NSPs? The answer appears to be a combination of the increase in the number of young people who inject drugs7 and the continued high incidence of HCV infection among IDUs, and in particular among young people who have recently started injecting drugs (around 20% of IDUs are infected with HCV within three years of commencing injecting).8 The heroin shortage in Australia beginning in 2000 may have interrupted the increase in the number of IDUs, but whether a shortage will persist is uncertain. It is too early to estimate the net costs and benefits of the heroin shortage, but one benefit has been the 25% drop in deaths from drug overdose between 1999 and 2000.9

Finally, what should be done? Alternative strategies that need to be considered (in combination with NSPs) include medically supervised injecting centres, drug law reform, a trial of medically supervised prescription of illicit drugs for treating refractory drug users, introduction of harm-minimisation strategies into prisons, and education programs to encourage people who do or might inject drugs to consider non-injecting routes of administration. Such strategies must be debated in the community and properly evaluated. As each new HCV infection is estimated to cost healthcare systems more than $10 000,10 such strategies make sound health and financial sense. Many IDUs ultimately abandon injecting illicit drugs — it is in everyone's interests that they are still healthy when they do so, to maximise the likelihood that they will lead normal and useful lives.

With the recent confirmation of the effectiveness of NSPs in preventing HIV transmission, it is important that society continues to support these programs. This may appear self-evident, but closing down NSP centres is often politically popular, especially in marginal electorates in tight elections. We must not become complacent just because a feared epidemic of HIV among IDUs has not eventuated. There is no guarantee that it will not happen in the future, as has been seen in some other countries.11 Any loss of resolve in the commitment to NSPs increases the likelihood of an HIV epidemic among IDUs, with potentially disastrous consequences for other at-risk populations (such as female sex workers or Indigenous Australians) and thence for the wider community.