Usually the issue with having injections etc only arises if you're at risk of lymphodema on that side. It doesn't usually apply after WLEs for DCIS as we don't usually have any lymph nodes sampled. As far as I know there's nothing to worry about in terms of having injections or blood tests on that side unless you did have a sentinel node excision.
I did have a flu jab after mine, and the nurse was careful to ask me about lymphodoema, so they do take it into account.
Hope things have improved now.