Hi Paul, That’s a discussion I’ve had many times with my transplant doctor. My donor was a 20 year old male from the U.S. From my perspective, 5 years later at 70 years of age, I quite frankly feel like I’m in my 20s! I’m healthy and incredibly fit. I joke about having super human powers because if I get a cut or burn on my hand, it heals within a very short span of time. So I can’t help but think that I have a really strong, new immune system.
Before AML and transplant, I was rarely ever ill in my life and that remains true today. In the 5 years since my transplant I’ve been very judicious wearing my mask, avoiding high exposure events and since that time I’ve had no infections at all. I’m quite happy not tempting fate. ☺️

However, from what I’ve learned, my new system, no matter how strong it is, will never be as robust as ‘the factory installed model’.
There’s no way to fully measure the strength of my immune system. I’ve had all of my childhood, adolescent and adult vaccinations. However, it’s been noted in numerous studies, after vaccinations in stem cell transplant patients, that generation of antibodies is markedly lower. There’s no information that I’ve seen as to what the B and T Cell responses are. So this remains an unknown.

Another reason I don’t risk developing a serious illness is because of a side effect of transplant referred to as GVHD. Graft vs host disease. My new immune system (the graft), is the controller of all things! It looks at my body (host) as the invader. So if there is a source of inflammation the immune response is to rush to the rescue. This can cause the system to go into high alert and the results or level of response can be unpredictable. Small things can become potentially life threatening. So it’s better to be safe than sorry. ☺️