Economic value of a therapeutic Chagas vaccine for indeterminate and Chagasic cardiomyopathy patients

Background: Therapeutic vaccines to prevent Chagas disease progression to cardiomyopathy are under development because the only available medications (benznidazole and nifurtimox) are limited by their efficacy, long treatment course, and side effects. Better understanding the potential clinical and economic value of such vaccines can help guide development and implementation. Methods: We developed a computational Chagas Markov model to evaluate the clinical and economic value of a therapeutic vaccine given in conjunction with benznidazole in indeterminate and chronic Chagas patients. Scenarios explored the vaccine's impact on reducing drug treatment dosage, duration, and adverse events, and risk of disease progression. Results: When administering standard-of-care benznidazole to 1000 indeterminate patients, 148 discontinued treatment and 219 progressed to chronic disease, resulting in 119 Chagas-related deaths and 2293 DALYs, costing $18.9 million in lifetime societal costs. Compared to benznidazole-only, therapeutic vaccination administered with benznidazole (25–75% reduction in standard dose and duration), resulted in 37–111 more patients (of 1000) completing treatment, preventing 11–219 patients from progressing, 6–120 deaths, and 108–2229 DALYs (5–100% progression risk reduction), saving ≤$16,171 per patient. When vaccinating determinate Kuschnir class 1 Chagas patients, 10–197 fewer patients further progressed compared to benznidazole-only, averting 11–228 deaths and 144–3037 DALYs (5–100% progression risk reduction), saving ≤$34,059 per person. When vaccinating Kuschnir class 2 patients, 13–279 fewer progressed (279 with benznidazole-only), averting 13–692 deaths and 283–10,785 DALYs (5–100% progression risk reduction), saving ≤$89,759. Therapeutic vaccination was dominant (saved costs and provided health benefits) with ≥ 5% progression risk reduction, except when only reducing drug treatment regimen and adverse events, but remained cost-effective when costing <$200. Conclusions: Our study helps outline the thresholds at which a therapeutic Chagas vaccine may be cost-effective (e.g., <5% reduction in preventing cardiac progression, 25% reduction in benznidazole treatment doses and duration) and cost-saving (e.g., ≥5% and 25%, respectively).