Even though I have cancer, I am currently NED (No evidence of disease) so my body is not actively (as far as we know) fighting cancer. I have a manual check-up every 3 months to confirm that the sarcoma is not regrowing locally (which would require more surgery or amputation) and radiation - and any lumps and bumps that develop between visits can trigger more scans or treatment sooner than 3 months. (I had one scare at 4 months post-diagnosis, which required intermetiate scans.) I also have lung scans every 3 months because the lungs are where the cancer will metastasize to.
Although I have not had antibody tests to confirm a normal immune response, I was not on immune-suppressing treatment at the time I was vaccinated (so I should have developed an immune response similar to someone of my age who doesn't have cancer). I am not currently on immune suppressing treatment (although if metastasis occurs I will be, with very little notice, because the cancer is so aggressive. I was diagnosed on December 4, and the first surgery took place on December 15. I would expect chemo on a similar time frame if lung mets are diagnosed.
So the risk you pose to me ** assuming the sarcoma continues to behave ** is largely the same that you pose to anyone else: That you develop COVID as a breakthrough case - and pass that on to me - which might, in turn, cause me to become a breakthrough case. The slight increased risk to me (beyond that to the general public) is that if you expose me and I am diagnosed with lung mets while I am still within the window of exposure from you the chemo-related immune suppression would make it harder for my body to fight back.
You do pose a greater risk to cancer patients who are on cancer treatments that suppress the immune system - either at the time of vaccination (so their immunity is not fully developed) or were put on it after vaccination and their bodies can't muster the immune response despite having the tools.
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