Estimating the impact of international funding reductions on harm reduction programmes for people who inject drugs: a comparative analysis of three high-burden countries: India, South Africa, and Nigeria.

Harm-reduction services for people who inject drugs (PWID) remain vulnerable due to political instability and reliance on external funding. As international donors reduce support, the sustainability of these programmes is increasingly uncertain. This study examines how different HIV financing structures influence the resilience of harm-reduction services in India, Nigeria, and South Africa.A retrospective comparative analysis was conducted using national programme reports, financial data, and global monitoring sources from 2014 to 2024. Trends in domestic and external funding were assessed alongside coverage of opioid substitution therapy and needle-syringe programmes. Hypothetical scenarios modelling 30% and 50% reductions in donor funding were used to evaluate potential impacts. The three countries show distinct financing profiles. India's predominantly domestically financed programme (approximately 93% under NACP-V) appears relatively resilient to external shocks. Nigeria's donor-dominated financing (96.1% in 2021) leaves PWID services highly vulnerable, while South Africa shows intermediate vulnerability, particularly in key-population prevention.A three-pillar framework focusing on financing structure, programme integration, and epidemic-equity alignment, is proposed to assess transition readiness. Strengthening these dimensions is critical to ensure that donor transitions do not undermine harm-reduction services and HIV control among PWID.