I developed Bells Palsy from a flu shot in 2016, and still have not fully recovered. I would never have taken it, except that it is mandatory for my work. Fortunately I have a lifetime exemption now.
If I weren’t a cancer survivor, I would have foregone the flu shot, except for this year. Unfortunately, a good case of the flu, like any other potentially severe illness, could trigger a resurgence of my cancer. The convention nowadays is that you’re never cured of your cancer; it’s just assumed to be dormant.