Examining epidemiological models and economic analyses of Typhoid Conjugate Vaccine: A scoping review

Typhoid remains a preventable disease that primarily affects low- and middle-income countries. We conducted a scoping review to synthesize evidence on the epidemiological models and economic analyses of typhoid conjugate vaccine (TCV), focusing on the cost of illness of typhoid, the cost of vaccination, cost-effectiveness, and public health benefits of TCV. A search was conducted across PubMed, Web of Science, International Health Technology Assessment, Scopus, and the National Health Service Economic Evaluation Database, following Arksey and OMalleyss framework. Screening and data extraction were managed using Covidence and an Excel-based template. Extracted data included study design, population, outcomes, model parameters, and cost-effectiveness data, converted to 2024, United States Dollars (USD) for comparability. Findings were summarized by key outcomes. The economic burden of typhoid varied by region, care type, and demographics. Direct medical costs ranged from USD 1.3 to USD 1543, direct non-medical costs varied from USD 1.3 to USD 60.1, and indirect costs ranged from USD 14.1 to USD 794. Cost of vaccination per dose ranged from USD 2.80 - USD 5.40 (India), USD 0.87 - USD 1.01 (Malawi), and USD 2.99 (Zimbabwe), while the cost of delivering the vaccine ranged from USD 0.48- USD 0.99 (financial) and USD 1.11 - USD 1.87 (economic) per dose. Models predicted 2-94% case reductions and 0-100% mortality reductions. Economic evaluations reported ICERs of USD 124 to USD 53,773 per DALY averted and USD - 4,251 to USD 103,344 per QALY gained, with high-incidence settings often resulting in cost savings. Sensitive parameters were typhoid incidence rate, vaccine efficacy, and vaccination costs. TCV introduction is influenced by disease burden, vaccination costs, and health outcomes, which vary by region. Cost-effectiveness depends on incidence, perspective, and vaccine strategy, emphasizing the need for context-specific evaluations. Targeted strategies, particularly in high-incidence and urban areas, are often cost-effective and sometimes cost-saving.