Effect of influenza vaccination on mortality and hospitalization in heart failure patients in a non-seasonal influenza transmission country

Background: The association of influenza vaccination and heart failure (HF) hospitalization and mortality in Thai HF patients is unknown. Objective: To investigate associations between influenza vaccination and all-cause mortality or HF hospitalization in HF patients. Methods: : We retrospectively reviewed medical records from two large tertiary care centers in Thailand (Ramathibodi hospital and Maharaj Nakorn Chiang Mai hospital) with newly diagnosed heart failure between 2013-2020 in an outpatient clinic. We examined the relationship between influenza vaccination and outcomes using a propensity-adjusted model. Results: : Of 588 patients, 181 (31%) received influenza vaccination. During a mean follow-up of 57 months, influenza vaccination was associated with a 56% reduction in the risk of HF hospitalization or death (HF hospitalization or all-cause death: HR 0.44; 95% CI 0.31-0.63; p <0.001) in unadjusted analysis. After propensity score adjustment, influenza vaccination though was not associated with reduced risk of all-cause death but associated with reduced risk of HF hospitalization (HR 0.39; 95%CI 0.26-0.58; p <0.001). Conclusions: : In patients with HF, influenza vaccination was associated with a reduced risk of HF hospitalization but not all-cause mortality.