I also experienced a PMR flare almost immediately after receiving the Covid vaccine. I took prednisone which worked very quickly to relieve the symptoms and then I was able to successfully taper off over a three-month period. I am now in remission. I agonized for weeks over whether to have the booster shot. My rheumatologist opined that if I did contract the virus I would have a worse outcome because of my reaction to the vaccine and thought I should go ahead with the shot and take prednisone again if needed. With much trepidation I scheduled the shot and was very pleased when I did not experience another flare of PMR. Later on, I did come down with the virus but had almost no symptoms. Everyone's journey is different and each individual must weigh the options and try to arrive at the best decision. I wish you luck and hope you achieve remission soon.