Influenza Vaccination and Ischemic Stroke Prevention

Seasonal influenza may transiently increase the risk of vascular events, including ischemic stroke (IS).1 Acute systemic inflammation may drive this relationship, possibly through endothelial dysfunction, atherosclerotic plaque instability, and a procoagulant state.2 It therefore stands to reason that influenza vaccination may diminish the associated stroke risk, but the evidence has been mixed. In 2 meta-analyses of observational studies, individuals who received the influenza vaccine were less likely to have a stroke, but the included studies were heterogenous, relatively small, and potentially limited by biases.3,4