The concern with vaccines is the immune stimulating affect of the adjuvant included in the vaccine to heighten an immune response to the vaccine to make it more effective. Since PMR is a condition caused by an excessive immune response, we have to be careful not to stimulate the immune system too much. Some adjuvants are worse than others and each of us responds to each adjuvant differently.

"Autoimmune/inflammatory syndrome induced by adjuvants"
"Adjuvants.... when added to vaccines they are meant to boost the effect and strongly stimulate the immune system. The response of the immune system can be unpredictable..."
https://academic.oup.com/cei/article/213/1/87/7071043
Each of us has to assess our own risks for catching anything being vaccinated for - it depends how exposed to others you are. I'm generally in favour of necessary vaccines, but haven't had any vaccinations since getting PMR over 2yrs ago. Instead, I avoid public places as much as possible and always wear a mask whenever it can't be avoided.