I'm just stuck!

It's flu shot time.
As I type this my arm has the odd soreness.
Now this part may sound a little weird.
I only started getting these in 1999.
It would have been very bad to bring flu home after that.
Well the "reason" I started is gone, yet I still get them?
The woman giving it was laughing that I was taking pictures.
She was a sport about it and held her other arm out of the way.
Sometimes the things I think of amazes even me.
Well I have a letter to write, so off I go ;-)