I wonder if some of this might also apply to my other autoimmune disorder. I have type 1 diabetes so this research is of interest to me for that and also the GPA we all share here.

The study reports that patients with type 1 diabetes who received just two doses of the BCG vaccine, spaced four weeks apart, achieved markedly lower A1c levels compared to the control group. This result was observed three years after the vaccine administration and continued for the next five years of follow-up.

This is the part of the study that might apply to GPA:
"The vaccine appears to influence the immune cell populations responsible for the autoimmune attack in type 1 diabetes. Specifically, they determined that the vaccine can exert epigenetic changes that result in a different CD4 T cell and regulatory T cell phenotype."

More details on this link if it works for you: Other wise google it if interested.