The effect of influenza vaccination on mortality and risk of hospitalization in patients with heart failure: A systematic review and meta-analysis

Background. Influenza is a major cause of morbidity and mortality in patients diagnosed with heart failure. The aim of this study was to evaluate the effectiveness of influenza vaccination in this population in terms of reduction in all-cause mortality and rate of hospitalization. Methods. We conducted a systematic review and meta-analysis using PubMed and EMBASE entries from January of 2000 through April 2018. Publication bias was examined using the Egger's regression test. Statistical heterogeneity was examined using the Higgins I2 statistic. Subgroup analyses were performed to examine the effect of vaccination during the influenza and noninfluenza seasons. Results. We identified 8 studies that included a total of 82 354 patients with heart failure. In patients with heart failure who were vaccinated against influenza, we found a reduced risk of all-cause mortality (hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.51-0.87). No evidence of publication bias was found, and the effect was more pronounced during influenza season (HR, 0.49; 95% CI, 0.30-0.69), compared with noninfluenza season (HR, 0.79; 95% CI, 0.68-0.89). In terms of heart failure hospitalizations, we did not identify a statistically significant difference between the cohorts (HR, 0.62; 95% CI, 0.00-1.23). Conclusions. Influenza vaccination was associated with a decreased risk of all-cause mortality in patients with heart failure, and this effect was more prominent during the influenza season.