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Decline in incidence of HIV and Hepatitis C virus infection among injecting drug users in Amsterdam; evidence for harm reduction?. Anneke de Vos 1 , Jannie van der Helm 2 , Amy Matser 2 , Maria Prins 2,3 , Mirjam Kretzschmar 1,4.
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Decline in incidence of HIV and Hepatitis C virus infection among injecting drug users in Amsterdam; evidence for harm reduction? Anneke de Vos1, Jannie van der Helm2, Amy Matser2, Maria Prins2,3, Mirjam Kretzschmar1,4 1. Julius Center, University Medical Centre Utrecht, Utrecht, The Netherlands. 2. Public Health Service, Amsterdam, the Netherlands 3. Academic Medical Center, University of Amsterdam (CINIMA), Amsterdam, the Netherlands 4. Centre for Infectious Disease Control, RIVM, Bilthoven, The Netherlands.
Amsterdam IDU • Cohort studies since 1985 (ACS) • HIV & HCV: very strong incidence decline • HIV: strong prevalence decline • introduction ~1980, peak ~1990 • Harm reduction from 1981 • opiate substitution (methadone) • needle exchange facilities
Amsterdam IDU • Changing demography • fewer new injectors • →aging population • Natural epidemic progression: • incidence ↔ prevalence • HIV-mortality ↔ population structure Matser et al. 2012
Can we explain disease time-trends by demographic dynamics, assuming no effects of harm reduction? Method: individual based simulation modeling Study description
Low risk Start injecting HCV+ Stop injecting Relapse injecting Recruitment ACS Stop injecting Death Modeled individuals • Injecting status • constant stop- and relapse-rates • ACS participation status • recruitment of current injectors • HIV & HCV status • Mortality-rate by: • age • time since HIV infection • HIV treatment (from 1997) • Risk behavior: high or low • No harm reduction
Results explained • Decline in HIV & HCV incidence • fewer ever-IDU still injecting • fits ACS data • due to a constant stop-rate + fewer new IDU • high-risk infected sooner → low-risk left at risk • HIV prevalence decline • high-risk IDU die faster → lowered population risk
Lowered risk? Introduction of cART Results improved? • cART introduction more gradual • better fit HIV prevalence decline • Harm reduction; risk decline by calendar-time • can explain slight HCV prevalence decline • similar results for risk decline with age! • strong effects on risk consistent but not necessary
Summary & conclusion • Main trends in HIV and HCV among Amsterdam IDU could be explained by demographic changes • Effects of harm reduction could not be disentangled from other causes Studies on the effects of harm reduction intervention should consider natural epidemic progression and demographics
Conducted within UCID – Utrecht Center for Infection Dynamics We thank RoelCoutinho We are grateful to the Amsterdam Cohort Studies Thank you Funded by: