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

Abstract

Influenza can exacerbate chronic coronary heart disease (CHD) and health policy recommends influenza vaccination in this patient group. However, the cost effectiveness of influenza vaccination in protecting CHD patients has not been well studied before especially in different disease severities. The Markov model of CHD progression concurrent with influenza infection was developed to quantify the life-time costs and health effects of the three influenza vaccination strategies in: 1) Angina patients; 2) Cardiac Arrest/Myocardial Infarction (CA/MI) patients; 3) CHD combined group, versus no influenza vaccination. Cost-effectiveness analysis (CEA) comparing between the three vaccination strategies was performed to assess the highest effectiveness from a societal perspective. Decision analysis software (TreeAge) was used to explore relative cost-effectiveness of influenza vaccination strategies. Deterministic and probabilistic analyses were performed to identify variables that influence the sensitivity of the result and the robustness of the study model. The results showed Incremental Cost Effectiveness (ICER) of vaccination in Angina patient, in CA/MI patients, and in CHD combined group as 8,420, 62,711 and 33,813 THB per QALY gained, respectively; therefore, the highest cost-effectiveness is vaccination in Angina patients. Considering willingness to pay (WTP) threshold at 100,000 THB per QALY as accepted by Thai National Formulary 2010, influenza vaccination in CHD combined group is the most optimal and should be recommended as it yielded highest QALYs gained while it is still within WTP threshold. The study results are in accordance with the current influenza vaccine recommendation, both international and Thailand. Influenza vaccine underutilization has been reported; therefore, strongly promoting the administration of influenza vaccination to CHD patients is highly recommended.