The role of depression in secondary HIV transmission among people who inject drugs in Vietnam: A mathematical modeling analysis

Abstract

Background: Among people who inject drugs (PWID), depression burden is high and may interfere with HIV prevention efforts. Although depression is known to affect injecting behaviors and HIV treatment, its overall impact on HIV transmission has not been quantified. Using mathematical modeling, we sought to estimate secondary HIV transmissions and identify differences by depression among PWID.

Methods: We analyzed longitudinal data from 455 PWID living with HIV in Vietnam during 2009-2013. Using a Bernoulli process model with individual-level viral load and behavioral data from baseline and 6-month follow-up visits, we estimated secondary HIV transmission events from participants to their potentially susceptible injecting partners. To evaluate differences by depression, we compared modeled transmissions per 1,000 PWID across depressive symptom categories (severe, mild, or no symptoms) in the three months before each visit.

Results: We estimated a median of 41.2 (2.5th, 97.5th percentiles: 33.2-49.2) secondary transmissions from all reported acts of sharing injection equipment with 833 injecting partners in the three months before baseline. Nearly half (41%) of modeled transmissions arose from fewer than 5% of participants in that period. Modeled transmissions per 1,000 PWID in that period were highest for severe depressive symptoms (100.4, 80.6-120.2) vs. mild (87.0, 68.2-109.4) or no symptoms (78.9, 63.4-94.1). Transmission estimates fell to near-zero at the 6-month visit.

Conclusions: Secondary transmissions were predicted to increase with depression severity, although most arose from a small number of participants. Our findings suggest that effective depression interventions could have the important added benefit of reducing HIV transmission among PWID.

Fig 1. Distribution of partner susceptibility and exposure to HIV, overall and by participant’s baseline depressive symptoms.

Percentages are based on the 833 partners reported by 455 participants at the baseline visit and the 251 partners reported by 377 participants at the 6-month visit. “Potentially susceptible” refers to partners with reported HIV-negative or unknown HIV status. Among potentially susceptible partners, “minimally exposed” had ≥1 sharing act with a participant who had suppressed viral load (<400 copies/ml). “More exposed” partners participated in ≥1 sharing act with a participant who had unsuppressed viral load (≥400 copies/ml).

Fig 2. Modeled secondary transmission events in the three months prior to baseline per 1,000 PWID living with HIV in each depressive symptom category.

Estimates from 2,500 model runs are plotted by type of sharing act (all sharing acts vs. only needle-/syringe-sharing). Colored regions show all 2,500 estimates, the black point is the median, and the vertical line extends from the 2.5^th to 97.5^th percentiles.

Fig 3. Modeled secondary transmission events in follow-up months 3–6 per 1,000 PWID living with HIV in each depressive symptom category.

Estimates from 2,500 model runs are plotted by type of sharing act (all sharing acts vs. only needle-/syringe-sharing). Colored regions show all 2,500 estimates, the black point is the median, and the vertical line extends from the 2.5^th to 97.5^th percentiles.