An Open Letter on Advancing HIV prevention: Augmenting an ecosystem-based approach to understand prevention decision-making.

In the last two decades, HIV programs have been able to avert millions of AIDS-related deaths and reduce HIV incidence. However, the 1.3 million new HIV infections in 2022 remain significantly above the UNAIDS target of fewer than 370,000 new infections by 2025. HIV programs worldwide also did not achieve the UN's 90-90-90 target for testing and treatment set for 2020. Within this broader picture, HIV continues to disproportionately affect key and at-risk populations, including gay men and other men who have sex with men, female sex workers, and adolescent girls and young women. As HIV incidence declines and biomedical advances continue, it will become critical for public-health practitioners to reach key and at-risk populations with prevention services and limit primary transmission. In this Open Letter, we focus on factors that influence uptake of HIV prevention products and thereby demand for HIV prevention products and services. These factors exist at three levels of the decision-making ecosystem - the individual level, interaction level and systemic level. We argue that approaching HIV prevention solely through the lens of these levels creates a static view of prevention decision-making. There is a need instead for a dynamic viewpoint that can mirror the changing contexts in which users find themselves and make prevention decisions. We demonstrate that the current ecosystem viewpoint is useful to understand the gaps that exist in program implementation, but does not provide adequate insights into the underlying behaviors that contribute to these gaps. To address this, we suggest an approach to include dynamic aspects of decision-making with factors that influence the individual's assessment of risk, their evaluation of the opportunities to use HIV prevention, and their effective use of prevention products.