Hello @golfbarmie, Welcome to Mayo Clinic Connect. Thank you for sharing your journey with GCA and PMR. My PMR is currently in remission but my rheumatologist was always concerned about the possibility of me also having GCA. When my PMR was active he was also checking me for symptoms of GCA. I've had both Pfizer COVID vaccines but fortunately no flares in my PMR.

There are a few other discussion for GCA that you might be interested in:
- Giant cell arteritis: https://connect.mayoclinic.org/discussion/giant-cell-arteritis-20c716/
- GCA (Giant Cell Arteritis) and PMR (polymyalgia rheumatica): https://connect.mayoclinic.org/discussion/temporal-arteritis-1/

Have you tried going down in your prednisone dosage by 1/2 mg? I had trouble tapering below 1 mg for my first occurrence of PMR and my rheumatologist suggested splitting 1 mg tablets to see if that helped tapering. So I went back and forth between 1 mg and 1/2 mg for six months before I was finally able to taper off with only minimal discomfort on my pain scale.