Opposite Directions: A Decade of Contrasting HIV and HCV Dynamics Among Injecting Drug Users in Mozambique

People who inject drugs (PWID) experience a high burden of HIV and hepatitis C virus (HCV) infection due to unsafe injection practices and limited access to harm-reduction services. In Mozambique, data on PWID remain limited. This study analyzed two rounds of biobehavioral surveys conducted in 2014 and 2023 in Maputo and Nampula to assess trends in HIV and HCV prevalence and to identify associated behavioral and structural factors. We compared unweighted prevalence estimates using descriptive analysis and applied multivariable logistic regression to examine independent associations with each infection and interaction effects with survey year. HIV prevalence declined across most demographic and behavioral groups. Among PWID aged [&ge;]25 years, prevalence decreased from 55.7% to 26.3%, and among men from 45.7% to 16.7% (both p < 0.001). Reductions were also observed among daily injectors (58.0% to 21.3%) and individuals reporting syringe sharing (75.0% to 21.8%). In Maputo, HIV prevalence declined from 56.6% to 28.0%, while the decrease in Nampula was not statistically significant. Age and female sex were strong predictors of HIV infection in the earlier survey, although the association with age weakened in 2023. HCV prevalence showed divergent trends. In Maputo, prevalence decreased from 49.3% to 18.7% (p < 0.001), whereas in Nampula it increased from 11.7% to 48.1% (p < 0.001). PWID aged 16-24 years experienced a fivefold increase in HCV prevalence. Interaction analysis demonstrated a significant rise in Nampula in 2023 (AOR 14.6; p < 0.001). Lower injection frequency and not sharing needles were protective factors for both HIV and HCV. These findings indicate a substantial reduction in HIV prevalence among PWID in Mozambique over the past decade, alongside an increase in HCV prevalence in specific geographic and age groups. The contrasting trends highlight the need for differentiated harm-reduction strategies, expansion of HCV prevention and treatment services, and tailored interventions for subgroups at elevated risk.