Influenza vaccine and survival in acute heart failure

Aims: Influenza vaccine is a well-recommended secondary prevention measure for improving survival in patients with coronary artery disease, but it has generally been less studied in heart failure. We ask whether having influenza vaccination is associated with survival among patients with acute heart failure (HF). Methods and results: This was a prospective population-based cohort study accompanied by an analysis of two cross-sectional population samples for external validation of baseline characteristics differences. We analysed all 1964 ambulatory patients with acute HF aged ≥50 years who were admitted to the Heart Failure Survey in Israel (HFSIS). We used the Israel Health Survey (IHS) 2009 and the Behavioural Risk Factor Surveillance System (BRFSS) 2003-2004 surveys (274 535 participants) for external validation. In the HFSIS, the multivariate-adjusted hazard ratios for in-hospital, 1 and 4 year mortality outcomes of influenza-vaccinated patients were 0.71 (P = 0.19), 0.81 (P = 0.04), and 0.83 (P = 0.006), respectively. In the IHS validation sample, a recent physician visit [odds ratio (OR) 1.61; 95% confidence interval (CI) 1.43-1.80] or having supplementary health insurance (OR 1.39; 95% CI 1.19-1.61) were associated with higher likelihood of being vaccinated against influenza. In the BRFSS validation sample, having > 1 healthcare providers (OR 2.31; 95% CI 2.22-2.40) or having any healthcare coverage were associated with higher likelihood of being vaccinated (OR 1.59; 95% CI 1.54-1.65). Conclusions: Influenza vaccine might improve survival among patients with acute HF. This association, however, could be affected by unmeasured confounding and bias due to baseline medical surveillance and socioeconomic differences between vaccinated and non-vaccinated patients.