Influenza vaccination and cardiovascular and respiratory outcomes in high-risk populations: an umbrella review of systematic reviews and meta-analyzes

BackgroundInfluenza infection is an important trigger of acute cardiovascular events and respiratory decompensation in vulnerable populations. Although influenza vaccination may reduce cardiopulmonary morbidity and mortality, the overall certainty and methodological reliability of the evidence remain unclear.ObjectiveTo synthesize and critically evaluate published systematic reviews and meta-analyses on the effectiveness and safety of influenza vaccination in populations at high risk of cardiovascular and respiratory complications.MethodsWe conducted an umbrella review of systematic reviews and meta-analyses identified through PubMed, Embase, and the Cochrane Library from inception to December 1, 2025.

Methodological quality was assessed using AMSTAR-2, evidence certainty using GRADE, and overlap of primary studies using citation matrices and corrected covered area (CCA). Given heterogeneity and review overlap, we performed a narrative synthesis and applied predefined rules to prioritize representative reviews.ResultsFourteen systematic reviews and meta-analyses were included.

The strongest evidence supported an association between influenza vaccination and reduced major cardiovascular risk, particularly major adverse cardiovascular events in patients with ischemic heart disease and acute coronary syndrome. Vaccination was also associated with reduced cardiovascular mortality and all-cause mortality in some high-risk populations.