Flu shot for baby

My son is 6 months and he is technically due for a flu shot that I don’t want him to have. Thing is my doctor just gives him injections and doesn’t tell me what they are or even asks if which ones I want him to have. The flu shot is the only one I think that is unnecessary at the moment. He isn’t in daycare. I’m a sahm and he’s my only child. We barely go out in public, and I rarely get sick. I don’t even get the flu shot. How do I politely tell him before hand I don’t want it for my son?