Basic demographic and clinical characteristics.

People living with HIV (PLHIV) who do not achieve viral suppression on antiretroviral therapy contribute to HIV transmission. Poor adherence is a major factor associated with high viral load (VL). Enhanced adherence counseling (EAC) is a targeted intervention to improve adherence and achieve viral suppression, but data on post-EAC outcomes in Zambia remain limited. This study assessed viral suppression and associated factors among PLHIV with unsuppressed VL after completion of EAC at University Teaching Hospital and Kanyama First-Level Hospital. This retrospective cohort study analyzed VL register data from 1st January 2021–31st December 2023. Baseline demographic, clinical, and laboratory data were collected, with follow-up VL measurements at three and 12 months post-EAC. The primary outcome was viral suppression at three months, defined as a VL < 200 copies/mL. Poisson regression with robust standard errors identified factors associated with suppression. Among 386 participants (median age 39 years, IQR: 31–47), 52.9% were female. The baseline VL was 21,600 copies/mL (IQR: 3,692–106,000). At three months post-EAC, 85% (330/386) achieved viral suppression, with 95.8% (316/330) maintaining suppression at 12 months. Viral rebound occurred in 4.2% (14/330). EAC delivered through both telephone and in-person methods increased suppression likelihood by 15% compared to those who received EAC in-person (physical) alone. Prior enrollment in six-month multi-month dispensing (MMD) was associated with a 23% increased likelihood of suppression compared to those who had never received MMD. Participants on tenofovir/lamivudine/dolutegravir were 29% more likely to suppress compared to those on zidovudine/lamivudine/dolutegravir. EAC modestly improves and sustains viral suppression among PLHIV with high viral loads. In-person and telephone-based EAC improved viral suppression by 15% compared to in-person alone. Other key factors influencing suppression were community-based delivery and prior six-month MMD. Findings highlight opportunities to integrate technology-enhanced adherence support and differentiated service delivery models to optimize HIV care outcomes.