Switzerland’s successful HIV prevention policy for IV drug users

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Switzerland’s pragmatic HIV prevention policy for intravenous drug users has been extremely successful. Medical Xpress reports that thousands of HIV infections and Aids cases have been prevented thanks to harm reduction measures, as shown by an analysis by the University of Zurich, the University Hospital Zurich and the Swiss HIV Cohort Study.

Researchers were able to document and quantify the success of measures taken for the prevention of HIV transmission through intravenous drug use in Switzerland, based on a mathematical model and detailed clinical, viral genetics and epidemiological data from the Swiss HIV Cohort Study.

Harm reduction measures such as needle exchanges, methadone programmes, supervised heroin programmes and contact and consultation services for drug users were all analysed.

Alex Marzel at the Institute of Medical Virology and his colleagues could demonstrate through their work that the measures in Switzerland had prevented a total of over 15,000 HIV infections among drug users. “Previously, the HIV epidemic frequently spilled over from intravenous drug users to the general population through sexual contact, meaning that the prevention measures in drug users also indirectly prevented more than 2,500 cases of HIV infection in people who do not use intravenous drugs,” says Professor Roger Kouyos, head of the study.

The report says Marzel et al’s evaluation not only documents the success of Switzerland’s pragmatic prevention policy, but also demonstrates that the harm reduction and prevention measures protect the general population from HIV infections. The analysis also demonstrates the value of the Swiss HIV Cohort Study. “Without the data from the cohort study, which began its work 30 years ago, it would not have been possible to produce such a detailed quantitative analysis,” says Kouyos.

Even without a detailed cost analysis, the economic implications are clear: based on a conservative estimate for the annual cost of treatment of CHF 20,000 per infection, the Swiss healthcare system would have spent an additional CHF 340m per year on the 17,000 prevented infections. These estimates thus indicate that prevention measures have saved over CHF 3.4bn in treatment costs over the last 10 years.

The report says the results of the data analysis demonstrate the outstanding effectiveness of the implemented harm reduction and prevention measures. Unfortunately, these are still considered controversial abroad, especially in Eastern Europe. In many countries, no prevention measures are offered at all.

“Many cases of the transmission of HIV through intravenous drug use could have probably been avoided by implementing the prevention measures. Considering that worldwide 1.7m intravenous drug users are HIV positive and around 30% of new infections outside sub-Saharan Africa occur in this risk group, this is another noteworthy result of our research project,” says Marzel.

The report says the Swiss HIV Cohort Study was founded over 30 years ago and has collected anonymous data from over 20,000 HIV positive individuals and a biobank containing over 1.5m blood samples. All university hospitals in Switzerland, as well as many cantonal hospitals and specialised domestic practitioners, contribute to the cohort study. The largest centre is located in Zurich.

Background: Human immunodeficiency virus (HIV) transmission among injecting drug users (IDUs) is increasing in the United States due to the recent opioid epidemic and is the leading mode of transmission in Eastern Europe.
Methods: To evaluate the overall impact of HIV harm reduction, we combined (1) data from the Swiss HIV Cohort Study and public sources with (2) a mathematical model expressed as a system of ordinary differential equations. The model reconstructs the national epidemic from the first case in 1980 until 2015. Phylogenetic cluster analysis of HIV-1 pol sequences was used to quantify the epidemic spillover from IDUs to the general population.
Results: Overall, harm reduction prevented 15903 (range, 15359–16448) HIV infections among IDUs until the end of 2015, 5446 acquired immune deficiency syndrome (AIDS) deaths (range, 5142–5752), and a peak HIV prevalence of 50.7%. Introduction of harm reduction 2 years earlier could have halved the epidemic, preventing 3161 (range, 822–5499) HIV infections and 1468 (range, 609–2326) AIDS deaths. Suddenly discontinuing all harm reduction in 2005 would have resulted in outbreak re-emergence with 1351 (range, 779–1925) additional HIV cases. Without harm reduction, the estimated additional number of heterosexuals infected by HIV-positive IDUs is estimated to have been 2540 (range, 2453–2627), which is equivalent to the total national reported incidence among heterosexuals in the period of 2007 to 2015.
Conclusions: Our results suggest that a paramount, population-level impact occurred because of the harm reduction package, beyond factors that can be explained by a reduction in risk behavior and a decrease in the number of drug users over time.

Alex Marzel, Katharina Kusejko, Rainer Weber, Philip Bruggmann, Andri Rauch, Jan A Roth, Enos Bernasconi, Alexandra Calmy, Matthias Cavassini, Matthias Hoffmann, Jürg Böni, Sabine Yerly, Thomas Klimkait, Matthieu Perreau, Huldrych F Günthard, Roger D Kouyos

Medical Xpress report
Open Forum Infectious Diseases abstract

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