The impact of investments in health systems: a rapid review of computational models.

Investments in health systems are essential for achieving effective sustainable and equitable health outcomes. However, national and global level stakeholders continue to grapple with how to quantify the impact of investments, its return of investment, and how to efficiently allocate health system inputs to improve health service delivery, health outputs and outcomes.This rapid review highlights the diverse computational models used to simulate investments in health systems strengthening. Our analysis revealed a range of methodologies, from agent-based simulations and dynamic computable general equilibrium models to structural equation models and the OneHealth Tool. Each model offers unique insights and has its strengths and limitations that need to be carefully considered for every scenario.A significant limitation across all models is the lack of external validation of the inputs and assumptions. The variability in data requirements and computational complexity also presents challenges in adapting these models to different contexts.To enhance the utility of these models, future research should focus on integrating ex-post impact evaluations and improving data collection to ensure accurate, context-specific inputs. Additionally, there is a need for better alignment between modelling results and policymaking processes to enhance the adoption and legitimacy among decision-makers of these tools.Overall, while current models provide valuable insights for planning and investment in health systems, addressing these limitations will be crucial for maximising their effectiveness and ensuring better-informed decision-making in health investments.