Atrial Fibrillation is a very common condition that can lead to strokes and other debilitating conditions.  This is a preliminary study that looks at a possible association between flu shots and decreased incidence of the development of atrial fibrillation.  This study was based on information from the Taiwan health study that took place over a ten year period.  This study discussed the theory that the influenza vaccine can potentially increase sympathetic tone and can lead to atrial fibrillation.  During this study, it appeared that the influenza vaccine may decrease the incidence of atrial fibrillation by 18%.  There are certain issues with the design of this study but none the less this is an interesting observation and hopefully there will be further studies that will either support or refute this study.

Source: The Association between Influenza Infection, Vaccination and Atrial Fibrillation: A Nationwide Case-Control Study – Heart Rhythm