Change in HIV incidence, prevalence and population viremia in Tanzania: findings from population-based HIV impact surveys in 2016–2017 and 2022–2023

Background Tanzania has over 1.5 million people living with HIV. Understanding changes in its HIV epidemic is critical to informing interventions and policies. We describe the state of Tanzania's HIV epidemic and progress toward epidemic control between 2016–2017 and 2022–2023. Methods Tanzania HIV Impact Surveys (THIS) 2016–2017 and 2022–2023 were nationally-representative, cross-sectional household-based surveys. Participants ≥15 years reported HIV testing and treatment histories and provided blood for serology. Weighted estimates of prevalence, incidence, and population viremia were calculated. Arithmetic differences and incidence percent ratios assessed change. Modified Poisson regression estimated adjusted prevalence ratios (aPR) for correlates of prevalence and population viremia. Findings Among participants ≥15 years with biomarker data (n = 31,579 in 2016–2017; n=33,663 in 2022–2023), 1831 and 1850 were living with HIV, respectively. Prevalence decreased from 4.9% [4.5–5.2] to 4.4% [4.1–4.7]. Incidence declined non-significantly from 0.24% [0.15–0.34] to 0.18% [0.09–0.26] and viremia from 2.8% [2.6–3.1] to 1.7% [1.5–1.8], a 41% reduction (aPR: 0.59 [0.52–0.67]). Higher prevalence and population viremia occurred among women and adults ≥25 years. Interpretation Between 2016–2017 and 2022–2023, prevalence and incidence were stable, while population viremia declined substantially, indicating progress toward HIV epidemic control. Continued targeted efforts are needed to reduce viremia among women and older adults. Funding Supported by President's Emergency Plan for AIDS Relief through the U.S. Centers for Disease Control and Prevention. The findings and conclusions are those of the authors and do not necessarily represent the official position of the funding agencies.