Disease and Economic Burden Averted by Hib Vaccination in 160 Countries: A Machine-Learning Analysis.

BACKGROUND: Global immunization against Haemophilus influenzae type b (Hib) has expanded with Gavi support. We estimated health, economic benefits, equity and cost-effectiveness in 159 countries (1990-2021), and projected effects of future introduction in China. METHODS: We used a random forest model to simulate counterfactual scenarios without Hib vaccine introduction in 159 countries (1990-2021) and to project effects of Hib vaccine introduction in China over the next decade. Ten variables were sourced from the World Bank and WHO; Hib disease burden estimates were from the Global Burden of Disease Study 2021. We compared counterfactual and actual results to quantify benefits, equity, and cost-effectiveness. Extensive uncertainty analyses were performed. RESULTS: Between 1990 and 2021, Hib immunization averted an estimated 1,321,123 (95% uncertainty interval [UI] 32,034-2,723,304) deaths and 90,973,504 (95% UI 3,573,718-197,099,799) disability-adjusted life-years globally. Greatest health and economic gains occurred in Africa and low- and middle-income countries (LMICs). Deaths averted decreased with later vaccine introduction (Pearson's r = -0.56). Vaccination did not improve health equity, and access remains limited in Africa and LMICs. Hib immunization was cost-saving in all countries. In China, introduction at any point in the next decade would provide health and economic benefits and be cost-effective, with earlier introduction yielding greater gains. CONCLUSIONS: Hib immunization provide substantial, cost-effective health and economic benefits globally. Persistent inequities in vaccine access for LMICs require targeted solutions. Policymakers in China should consider these findings for future vaccine introduction.