Earlier quoted context omitted.
I said that the immune system can cause damage. Vaccines have a very high safety standard as they are given to large numbers of healthy people, so the tolerance for serious side effects is very low. So the development there is very careful, and anything that looks too dangerous is hopefully caught in animal experiments or at worst at phase I. A well known example of how dangerous the immune system can be is the follo…
I have no doubts about the safety of vaccines in healthy people. I have some harmless curiosity about people who are not known to be healthy. How do you actually determine if someone is "too immunocompromised" for a vaccine? This must be a question with no good answer.
My understanding is that being too immunocompromised for a vaccine happens in two different ways:
1) the vaccine contains live virus and so there's danger that the weak immune system couldn't fight this off
2) the vaccine isn't live, so it's not dangerous on its own, but the immune system is too weak to recognize it, so it doesn't build any immunity to the real thing. (One doctor I was talking to said the mRNA ones should be good here, because your own body produces so much of the lookalikes that even a weak immune system should notice it - and then you're much better prepared to fight the real thing off faster.)
Only the first is immediately dangerous, so the standard seems to be to just stay away from those.
I'm not sure if much is commonly done for the second, in terms of looking for response, but you can get tests for measles antibodies and such, so that would probably be how?