9tails - ditto. While she was in the 'orsepital, she had a huge asthma attack and had to leave the 'orsepital quickly to live out. She never fully recovered!! Within a couple of years, unable to be ridden out of a walk, she had the onset of 'cushings' - within a couple of months she had what we think were strokes and had to be put down. Personally, I believe it was all through that flu jab reaction. Was never the same.
To add insult to injury, the vet sent me a huge bill for the op AND the flu jab!! I told 'em where to stick it!! Suggested they apply to the supplier of the vaccine for payment - which they did - and received it!!! If you bear in mind that she was at livery, the costs to me were enormous!!
I still miss her - but I do wish I hadn't listened to the vet and YO and had pts her much sooner. Living on a bare paddock (native pony) surrounded by horses with lush grass - was that kind I wonder? She was a top competition pony and in retrospect, I don't think her last few years had the quality of life I wished for her, although she was well looked after!!
Obviously, this is rare, most recover very quickly.
However, I did read somewhere, that researchers in the US have tied-in the increase in Cushings to the flu jab. Not much we can do about it really though I suppose. Especially those of us who compete!!