Meta-analysis links influenza vaccination to lower mortality in acute heart failure

AIMS: In patients with heart failure (HF) influenza vaccination has shown beneficial effects in preventing cardiac decompensations. However, no conclusive results have been achieved in the few studies that have evaluated the impact of vaccination during episodes of acute HF (AHF) decompensation. We conducted a systematic review and meta-analysis to determine the possible effects of influenza vaccination on all-cause mortality in patients diagnosed with AHF. METHODS: PubMed, Medline, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews databases were searched for longitudinal studies comparing patients with AHF vaccinated against influenza with unvaccinated patients. The primary outcome selected for meta-analysis was 1-year all-cause mortality, and secondary outcomes consisted of other outcomes reported in at least in two different studies. Statistical heterogeneity was determined by calculating the I² statistic. Individual adjusted results were pooled using a random effects model. Sensitivity analysis was run for the primary outcome by removing each individual study and then re-doing the meta-analysis. RESULTS: Up to 30 June 2025, five observational cohort studies examining the effect of influenza vaccination on 1-year all-cause mortality in AHF patients had been published. Statistical heterogeneity was low (I2 = 33.7%), meaning that between-study results were consistent. Pooled analysis of confounder-adjusted hazard ratio (HR) for all-cause mortality in vaccinated patients was 0.89 (95% CI 0.83-0.96) compared with unvaccinated patients. All sensitivity analyses rendered very similar results. In-hospital and 90-day mortality were reported in three and two studies and showed similar reductions in risk, with an adjusted odds ratio of 0.85, 95% CI 0.70-1.01, and adjusted HR of 0.86, 95% CI 0.76-0.96; respectively. Isolated data from single studies suggest no effect on hospitalization following discharge after the AHF episode. CONCLUSIONS: Influenza vaccination is associated with a lower short- and long-term all-cause mortality in patients with decompensated HF; however, as all the studies included in this meta-analysis were observational, these results could be subject to residual confounding and causality cannot be directly inferred from them.