Background: The current study aimed to evaluate the influence of regular annual influenza vaccinations on cardiovascular (CV) death and heart failure-related hospitalizations (HFrH) in stable outpatients with heart failure with reduced ejection fraction.
Methods: The Turkish research team-HF (TREAT-HF) is a network undertaking multicenter, observational cohort studies in HF. This study is a subgroup analysis of TREAT-HF outpatient cohorts who completed a questionnaire on influenza vaccination status and for whom follow-up data were available. A total of 656 patients with available follow-up data for CV death and HFrH including recurrent hospitalization were included in the study. Patients were classified into two groups: those who received regular influenza vaccination (40 %) and those who did not receive vaccination.
Results: During a mean follow-up of 15 ±6 months, 113 (18 %) patients had CV death and 471 (72 %) patients had at least one HFrH. The CV death rate was similar in both groups of patients (16 vs. 19 %, p = 0.37), whereas, HFrH and recurrent HFrH were significantly less frequently encountered in patients who received regular influenza vaccination than in those who did not receive vaccination (43 vs. 92 % and 16 vs. 66 %, p < 0.001, respectively). In a multivariate Cox proportional hazards model - in addition to a few clinical factors - vaccination status (HR = 0.30, 95 % CI = 0.17-0.51, p < 0.001) and graduation from university (HR = 0.35, 95 % CI = 0.17-0.72, p = 0.004) remained independently associated with the risk of recurrent HFrH.
Conclusion: Regular influenza vaccination does not influence CV deaths; however, it decreases HFrH including recurrent episodes of HFrH in outpatients with heart failure with reduced ejection fraction.
Keywords: Heart failure; Hospitalization; Influenza; Outpatients; Vaccination.