Influenza is a contributor to A-fib in some. My daughter had a bad case of pneumonia just before the US Thanksgiving and coincidental startwdnup with A-fib. Now she's on 200mg of Flecainide, along with Cardizem, and Atenolol. Consider the possibility that the vaccine isn't causing the A-fib, but the resulting immune response is triggering something. I know, same difference. But I wouldn't necessarily place the blame directly on something IN the vaccine.