Same story with me, PMR hit me hard for the first time in December 2021, right after my flu and covid booster shots in late October 2021. I am currently on my 4th declining prednisone regimen as each time I moved from 10 mg to 9 mg the pain would come back. My Rheumatologist said they have enough data to say that the booster was likely not the cause of my PMR (I would have eventually got it), but certainly it triggered an earlier reaction.