Modelling the impact of HIV and HCV prevention and treatment interventions for people who inject drugs in Dar es Salaam, Tanzania

Research output: Contribution to journalArticle (Academic Journal)peer-review


Introduction: People who inject drugs (PWID) in Dar es Salaam, Tanzania, have a high prevalence of HIV and hepatitis C virus (HCV). While needle and syringe programmes (NSP), opioid agonist therapy (OAT) and anti-retroviral therapy (ART) are available in Tanzania, their coverage is sub-optimal. We assess the impact of existing and scaled up harm reduction (HR) interventions on HIV and HCV transmission among PWID in Dar es Salaam.

Methods: An HIV and HCV transmission model among PWID in Tanzania was calibrated to data over 2006-2018 on HIV (~30% and ~67% prevalence in males and females in 2011) and HCV prevalence (~16% in 2017), numbers on HR interventions (5254 ever on OAT in 2018, 766-1479 accessing NSP in 2017) and ART coverage (63.1% in 2015). We evaluated the impact of existing interventions in 2019 and impact by 2030 of scaling-up the coverage of OAT (to 50% of PWID), NSP (75%, both combined termed ‘full HR’), and ART (81% with 90% virally suppressed) from 2019, reducing sexual HIV transmission by 50%, and/or HCV-treating 10% of PWID infected with HCV annually.

Results: The model projects HIV and HCV prevalence of 19.0% (95% credibility interval: 16.4–21.2%) and 41.0% (24.4–49.0%) in 2019, respectively. For HIV, 24.6% (13.6–32.6%) and 70.3% (59.3–77.1%) of incident infections amongst male and female PWID are sexually transmitted, respectively. Due to their low coverage (22.8% for OAT, 16.3% for NSP in 2019), OAT and NSP averted 20.4% (12.9-24.7%) of HIV infections and 21.7% (17.0-25.2%) of HCV infections in 2019. Existing ART (68.5% coverage by 2019) averted 48.1% (29.7–64.3%) of HIV infections in 2019. Scaling up to full HR will reduce HIV and HCV incidence by 62.6% (52.5–74.0%) and 81.4% (56.7–81.4%), respectively, over 2019-2030; scaled up ART alongside full HR will decrease HIV incidence by 66.8% (55.6–77.5%), increasing to 81.5% (73.7–87.5%) when sexual risk is also reduced. HCV-treatment alongside full HR will decrease HCV incidence by 92.4% (80.7–95.8%) by 2030.

Conclusions: Combination interventions including sexual risk reduction and HCV treatment are needed to eliminate HCV and HIV among PWID in Tanzania.
Original languageEnglish
JournalJournal of the International AIDS Society
Publication statusAccepted/In press - 19 Aug 2021


  • hepatitis C virus
  • HIV
  • people who inject drugs
  • mathematical modelling
  • Dar es Salaam
  • Tanzania


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