Influenza vaccination in patients with heart failure: a systematic review and meta-analysis of observational studies

Objective Despite the progression of treatments over decades, heart failure (HF) is a disease with high morbidity, mortality and economic burden. Influenza infection is an important trigger for cardiovascular (CV) events, including HF. Influenza vaccination has been seen to reduce the risk of CV mortality in patients with coronary disease, but the effect in patients with HF is still unclear. Therefore, we conducted a systematic review to evaluate the effect of influenza vaccination in the morbimortality of patients with HF. Methods MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Health Technology Assessment and PsycINFO databases (December 2018) were searched for longitudinal studies evaluating influenza vaccination compared with a non-vaccination control group in patients with HF. The risk of bias was assessed according to the ROBINS-I tool. We performed a random-effects meta-analysis to estimate the pooled HRs with 95% CIs, and heterogeneity was evaluated using the I 2 statistics. Results Six cohort studies evaluating 179 158 patients with HF were included in the meta-analysis. Influenza vaccination was associated with a lower risk of all-cause mortality (HR=0.83; 95% CI 0.76 to 0.91; I 2 =75%). The effect of the influenza vaccination was not statistically significant in a pooled analysis of CV mortality (HR=0.92, 95% CI 0.73 to 1.15; 2 studies) and of all-cause hospitalisations (HR=1.01, 95% CI 0.92 to 1.11; 2 studies). The majority of outcomes in the included studies had a serious risk of bias and almost all evaluated outcomes had very low Grading of Recommendation, Assessment, Development and Evaluation (GRADE) evidence. Conclusions Influenza vaccination was associated with a significant decrease in all-cause mortality risk in patients with HF.