Older family member insists the last COVID booster gave her 'brain fog'

[meadowlander]

20. The point of the vaccine is to trigger an immune response.

The fatigue and aches and chills are actually the immune system working, not the vaccine itself causing symptoms. So it seems plausible that the inflammation and demand on energy caused by her immune response is making her feel a little brain foggy or it could just be fatigue showing up as mental tiredness as well as physical aches and pains.

I was absolutely knackered and had chills and muscles aches after each vaccine dose. "Brain fog" is pretty subjective and it's hard to separate it out from perimenopause, depression, post-concussion symptoms, etc.

It's all a matter of degree. I'd be inclined to take on face value that she felt tired and not on top of her game mentally and that that could be caused in part by her response to the vaccine. I'd point out though that that's not a good reason not to get vaccinated or boosted or to discourage other people from doing so. If she got "brain fog" from her response to the vaccine imagine how much worse it would be from her response to the actual virus.