Cost-utility evaluation of influenza vaccination in patients with existing coronary heart diseases in Thailand

Abstract

Background: Influenza can exacerbate chronic coronary heart diseases (CHD) and health policy recommends influenza vaccination in this population group. However, cost effectiveness of influenza vaccination in protecting CHD population has not been, to our knowledge, well studied before especially in CHD patients with different disease severities. Objectives: To assess life-time cost utility of influenza vaccination in CHD patients either with angina and/or cardiac arrest/myocardial infarction (CA/MI) and to identify the most cost-effective influenza vaccination strategies. Method: The Markov model of CHD progression concurrent with the influenza infection was developed to quantify life-time costs and health effects of the three influenza vaccination strategies compared with no influenza vaccination (base case): (1) influenza vaccination in all CHD patients, (2) influenza vaccination in CA/MI patients-only, and (3) influenza vaccination in angina patients-only. The cost-effectiveness analysis (CEA) was based on the societal perspective. Deterministic and probabilistic sensitivity analyses were performed to identify variables that influence the sensitivity of the results and examine the effects of model parameters uncertainty, respectively. Results: For the base case, the expected value (EV) results of no influenza vaccination, influenza vaccination in all CHD groups, influenza vaccination in angina patients, and influenza vaccination in CA/MI are 346,437 Thai baht (THB) yielded 18.26 Quality adjusted life year (QALYs), 454,664 THB yielded 21.46 QALYs, 360,786 THB yielded 19.96 QALYs, and 437,901 THB yielded 19.72 QALYs; respectively. CEA graph comparing all influenza vaccination strategies shows that vaccination in all CHD patients groups and angina patients are in the costeffectiveness frontier, but not influenza vaccination in CA/MI patients. The cost-effectiveness rankings report shows that the willingness-to-pay (WTP) threshold (100,000 THB) is greater than the incremental cost effectiveness ratio (ICER) of vaccination in all CHD groups (ICER = 33,813 THB per QALY gained) and angina group (8,420 THB per QALY gained) and therefore the vaccination in all CHD groups, which is more expensive, but more effective would be recommended. The deterministic sensitivity analysis shows the most influential parameters driving the cost-effectiveness of vaccination strategies are the effect of influenza vaccination on CHD both for acute myocardial infarction and cardiovascular death, respectively. The probabilistic sensitivity analysis shows the same influenza strategy recommendation (vaccination in all CHD groups) as the base case analysis. Conclusion: From a societal perspective, influenza vaccination in all CHD groups is recommended. The information from economic modeling should be confirmed by primary economic research. Keywords: Coronary heart disease, cost-utility, influenza vaccine, Markov model, Thailand