I think it’s pretty standard that any vaccination can make some people feel a bit tired and ropey because it is triggering the immune system into life, and so there are mind blowing processes going on inside these wonderful bodies of ours, using energy, creating inflammatory responses etc that can affect people differently.
It is impossible to get the flu from a flu jab.
However, I believe that if you have something lurking in the background, such as a mild cold, that can worsen slightly because the body’s immune response gets diverted to the new ‘threat’ demanded by the vaccine. It’s all fascinating stuff that blows my mind!
Anyway, I might be wrong but that’s my very basic understanding of things.