There is a difference between "immune regulators" and "immune enhancers or boosters" and a big difference in individual response.
Regulators act to "level out" the immune response, make it more appropriate if you will, so that antibodies can still be formed against harmful organisms, but hopefully there is limited activity against benign or helpful organisms (like our own tissue)
Boosters do just that, boost the response to everything.
Each person with autoimmune disease responds to the regulators dependent on the actual cellular makeup of their disease, I know things like Echinacea are generally a problem for all AI sufferers, but some (like me) have issues with Vitamin C, too, so it's kind of trial and error as to how we will react to any immune modulating substance.
Vitamin D has been recommended as possible protection from COVID, citing deficiency in almost all tested cases, and it is also strongly recommended in AI.
Vaccines are another issue entirely. Their function is to activate against specific organisms, and produce antibodies against that one organism. There are some theories about certain immune mediated diseases like Sarcoidosis and Diabetes (which as yet have no unique identifying autoantibodies) being the result of a mis-reading of the organisms which cause Coxsacki virus antibodies, but as far as I'm aware that is still theoretical.
That probably makes the whole issue even more confusing, I'm sorry.
