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

Author: Fraser H, Stone J, Makyao N, Soriano MA, Sambu V, Mfisi P, Makere N, Luhman N, Nouvellet M, Ragi A, Mundia B, Vickerman P

Theme: Epidemiology & Public Health Research Year: 2019

Background: People who inject drugs (PWID) in Dar es Salaam, Tanzania, have high HIV and hepatitis
C virus (HCV) prevalence. Harm reduction interventions (HR: needle and syringe programmes (NSP)
and opioid substitution therapy (OST)) have existed in Dar es Salaam since 2011, with antiretroviral
treatment (ART) initiating in 2004. We model the impact of existing and scaled-up interventions
among PWID in Dar es Salaam.
Methods: We developed a dynamic HIV and HCV transmission model amongst PWID, calibrated to
data from Dar es Salaam on trends of HIV (~30% and ~67% in males and females respectively in 2011)
and HCV prevalence (~16% in 2017), HR intervention coverage, and ART coverage among PWID (63.1%
in 2015). We estimate the impact of existing interventions and impact by 2030 of scaling-up OST
(27.7% to 50% of PWID) and NSP (11.9% to 75% -‘full HR’), HCV-treating 10% of HCV-infected PWID
annually and increasing ART coverage to 90/90/90.
Results: The model projects HCV and HIV incidence are 9.9/100pyr and 0.6/100pyr in 2019,
respectively. Due to low coverage, OST and NSP has had low impact to date, averting 6.0%
(95%CrI:5.2–7.1%) and 6.7% (95%CrI:4.6–9.5%) of HIV and HCV infections, respectively, since 2011. In
contrast, ART (65.5% coverage in 2019) has averted 17.6% (95%CrI:14.5–20.3%) of HIV infections since
2004. Full HR is projected to reduce HCV and HIV incidence by 24.8% (95%CrI:18.9–31.6%) and 36.8%
(95%CrI: 25.4–47.0%) over 2019-2030, respectively. If ART and HCV treatment is scaled up alongside
‘full HR’, HCV incidence could decrease by 64.9% (95%CrI:62.0–68.5%) and HIV incidence by 50.9%
(95%CrI:42.8–58.5%) by 2030.
Conclusion: Existing harm reduction interventions and ART have impacted on HIV and HCV
transmission among PWID in Tanzania. However, further scale-up with HCV treatment is needed to
move Tanzania towards eliminating HCV and HIV among PWID.
Disclosure of interest: PV has received unrestricted research grants from Gilead unrelated to this
work. HF has received an honorarium from MSD unrelated to this work. JS has received a conference
attendance sponsorship form Gilead unrelated to this work.

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