@AndsLee I got mine in Tesco 4 weeks today.
I actually felt very slightly achey, around a 2/10 if that helps, for 2 days then nothing.
In comparison, I caught a virus the second week the DC went back to school, around 9 DC were off with it, mine went to a mild Pneumonia 
It took me 3 weeks to get over that, It was absolutely awful. Full on bed rest, no appetite, chest pain etc.
I know we can't avoid these things, but knowing we have had the flu jab makes me feel protected somewhat now.