Myocardial infarction, stroke, and sudden cardiac death may be prevented by influenza vaccination.

Acute myocardial infarction (AMI) and atherothrombotic stroke share a common pathogenesis involving disrupted atherosclerotic plaque and intravascular thrombosis. Both AMI and stroke have their peak incidence in winter months. Similarly, the incidence of upper respiratory infections (URIs), 38% of which are due to influenza, also peaks in winter (November and December). URIs result in many biochemical, cellular, and hemostatic changes that could predispose to plaque disruption and thrombosis. Infections, particularly URIs, frequently precede AMI and stroke. Up to 16% of persons older than 60 years of age experience a URI each year. Nineteen percent of those suffering an AMI recall a URI in the 2 weeks prior to their event. Three epidemiologic and one small clinical trial suggest that influenza vaccination is associated with a 50% reduction in incidence of sudden cardiac death, AMI, and ischemic stroke. Influenza vaccine is extremely safe and has a 50% efficacy. Theoretically, up to 104,500 AMIs and 192,000 nonembolic ischemic strokes could be prevented each year by influenza vaccination.