The Health Interventions Impact Calculator (HIIC): scaling up web-based access to proportional multistate lifetable analyses of avoidable burden, health gain and economic impacts.

Health metrics and modelling capacity have expanded to address present burden and burden attributable to risk factors in the past. There remains a gap in accessible tools that estimate avoidable burden; --that is, the future health and economic impacts of preventive and treatment interventions. This paper describes and demonstrates the Health Interventions Impact Calculator (HIIC), a free web-based analysis and visualisation tool that allows for rapid estimation of the future health and economic impacts of user-specified intervention scenarios for multiple diseases and risk factors. HIIC draws on precomputed outputs from the Scalable Health Intervention Evaluation programme (SHINE) proportional multistate lifetable (PMSLT) models. Users define an intervention scenario by specifying intervention timing, target population, intervention cost, and then modifying either disease rates or risk factor exposures. HIIC currently reports outcomes as differences between a business-as-usual (BAU) baseline and the intervention scenario, including health-adjusted life years (HALYs), deaths averted, health system expenditure and income impacts, for Australia. Outputs are presented through interactive dashboard visualisations and downloadable results. Three example intervention scenarios for Australia are presented: a 10% reduction in ischemic heart disease incidence, a 10% reduction in cervical cancer case fatality rate, and a BMI reduction of 2.5 kg/m{superscript 2} toward the theoretical minimum risk exposure level (TMREL). Across examples, HIIC generates 10-, 20-, and 40-year projections for health gains, mortality displacement over time, and economic impacts. A comparison of interventions based on cost-effectiveness shows how incremental costs and HALYs gained relative to BAU can differ substantially across intervention types, reflecting both intervention design and the level and trajectory of baseline burden. HIIC is a world-first accessible framework for standardised comparison of intervention scenarios against BAU that will soon be available for all countries. By linking risk factor and disease trajectory changes to health and economic outcomes within a consistent modelling structure, HIIC can inform transparent and reproducible priority setting for decision makers and researchers alike. Author SummaryDecision-makers need to determine which health interventions offer the greatest health gain for the resources invested, but comparing different options has been difficult. While we can measure current disease burden and past impacts, accessible tools for estimating what could be avoided in the future through new interventions have been lacking. We created a free online tool called the Health Interventions Impact Calculator that allows users to explore future scenarios for health interventions. Users enter details about a proposed intervention, such as reducing obesity, improving disease screening, or enhancing treatment, and the tool estimates future outcomes: deaths averted; health improvements, and costs over the next 10, 20, or 40 years. The tool compares each scenario against a business-as-usual future to show what additional benefits the intervention might achieve. We demonstrated this using three examples in Australia: a body-mass index intervention, a heart disease prevention intervention, and improvements to cervical cancer treatment. Currently available for Australia with over 200,000 ready-to-use scenarios and expanding worldwide in 2026, this tool provides researchers, health organizations, and policymakers with a standardised way to rapidly estimate and compare the future impact of different health interventions, supporting evidence-based decisions about where to invest limited resources.