Trends in HIV Viral Suppression in the POP-UP Low Barrier Care Program for People with HIV Experiencing Homelessness or Unstable Housing

Abstract Background HIV viral suppression remains suboptimal among people with HIV (PWH) facing barriers such as homelessness, substance use, and mental health disorders. In 2019, Ward 86 launched the POP-UP program, a low-barrier HIV care model serving PWH with unstable housing and difficulty engaging in care. In 2021, we introduced long-acting antiretroviral therapy (LA-ART) including for PWH unable to attain viral suppression on oral ART. This study evaluates temporal trends in viral suppression and mortality within POP-UP. Methods We conducted a retrospective cohort study of PWH enrolled in POP-UP between August 2019 and December 2024. Eligibility included viremia (HIV viral load ≥200 copies/mL) or being off ART, homelessness/unstable housing, and difficulty engaging in care. Criteria later expanded to include PWH with severe mental health or substance use disorders. Primary outcomes were viral suppression (<200 copies/mL) and mortality. Results Among 241 PWH ever enrolled in POP-UP, 86% attained viral suppression at least once during follow-up. Cross-sectional viral suppression was 47% in August 2019 (eight months after program inception) and increased to 64% in December 2024. By December 2024, 46% of suppressed patients were on LA-ART. Mortality declined from 8.8/100 person-years in 2020 to 2.6/100 person-years in 2024, with reductions in both AIDS-related and overdose deaths. Conclusions The POP-UP program improved viral suppression and may have reduced mortality among PWH with substantial barriers to care. Improvements were likely driven by integration of LA-ART and continued quality improvement. Persistent viremia within the program highlights the need for additional strategies to address structural and psychosocial barriers.