Cost-effectiveness of annual trivalent inactivated influenza vaccine program by age and risk status

Background The study was aimed to evaluate the cost-effectiveness of annual trivalent inactivated influenza vaccine (IIV3) under the context of Zhejiang province. Methods A state transition simulation model was constructed to estimate the health and economic outcomes of IIV3 vaccination compared to no vaccination for hypothetical cohorts of Zhejiang province stratified by age and risk status. Model input parameters were derived from multiple sources. The analysis used societal perspectives and a one-year time horizon, and permanent outcomes were also included. The primary outcome was the incremental cost-effectiveness ratio (ICER), with expression of US dollars per quality adjusted life years (QALYs) gained. Results In non-high risk subgroups, the ICER ranged from $6268/QALY(adults aged 50–64 years) to $11260/QALY (children aged from 6 months to 4 years). In high risk subgroups, the ICER ranged from cost-saving (adults aged ≥ 65 years) to $5260/QALY (children aged from 6 months to 4 years). Results were most sensitive to changes in the probability of influenza illness, vaccine effectiveness, probability of systematic reactions for adults aged 18–49 years with non-high risk status, while were most sensitive to changes in probability of influenza illness, cost of hospitalization, probability of death for the same subgroup. Conclusions Our findings indicated the ICERs of annual influenza vaccination varied by age and risk status but was less than one time of the Gross Domestic Product (GDP) per capita of Zhejiang province ($17745 in 2023), which remained cost-effective for all-age and different risk status groups from a societal perspective.