Independent effect of influenza vaccination on all-cause mortality in critically ill patients with atrial fibrillation: A retrospective study from the MIMIC-IV database

OBJECTIVE: Atrial fibrillation (AF) is common in critically ill patients and associated with higher mortality. The impact of influenza vaccination on all-cause mortality in this population is unclear. This study evaluates the effect of influenza vaccination on mortality in critically ill AF patients. METHODS: A retrospective cohort analysis was conducted using the MIMIC-IV database. The effect of influenza vaccination on mortality was assessed using Kaplan-Meier survival curves and Cox proportional hazards models, adjusted for confounders. Inverse probability of treatment weighting (IPTW) and propensity score matching (PSM) were used to minimize selection bias. Subgroup analyses examined clinical characteristics among AF patients in the intensive care unit (ICU). RESULTS: Among 12,137 ICU AF patients, 6554 (54.0 %) received the influenza vaccine. Vaccination was associated with reduced all-cause mortality (28-day hazard ratio [HR] = 0.79, 90-day HR = 0.83, 365-day HR = 0.84; all p-values <0.001). After PSM and covariate adjustment, influenza vaccination remained an independent predictor of better outcomes (28-day HR = 0.83, 90-day HR = 0.82, 365-day HR = 0.84; all p-values <0.001). These findings were consistent in IPTW analyses. Subgroup analyses showed greater benefits in elderly, hypertensive, and non-paroxysmal AF patients. CONCLUSION: Influenza vaccination is associated with improved survival in critically ill AF patients. These findings support vaccination as a crucial protective measure for high-risk AF patients in the ICU.