The Immune System after Chemo

Back in my post about finishing chemo, I mentioned the possibility of needing to have childhood immunizations redone. As I have mentioned on numerous occasions, chemo gives the immune system a beating. The worst of the cycles wiped it out to trace levels during the second week, which led to hospital trips upon getting sick. I only escaped this fate in the first two cycles, where I bounced back by Thursday of week 2, but the subsequent "bag" cycles (3, 6, 9, 12, 15) all ended up including hospital stays, and I didn't bounce back until the beginning of week 3.

But there are long term effects as well. One thing is that chemo carries with it an elevated risk of developing acute myeloid leukemia. Acute leukemia involves the bone marrow rapidly producing cancerous white blood cells. While this can happen to anyone, chemo ups the risk. The period of elevated risk lasts for about 10 years. Regular complete blood counts are done to catch this early if it does happen.

A lot more common is that acquired immunity to some diseases is lost. This is not just a concern during treatment itself. The cells killed by chemo include ones that produce antibodies that help fight diseases. So if enough of these cells die, the immunity given by these antibodies is lost even after treatment. But as the immune system needs time to recover for a vaccine to stimulate a proper immune response, so reimmunization cannot happen right away. In my case, the process took almost a year.

At the 6 month scan (September 2014), I was given a few blood tests to check my immune function and see what immunities I still had. The results of these tests determined whether I could stop taking the bactrim antibiotic for pneumonia prevention that I'd started back when I started chemo, what vaccines I would need again, and when I could get them. The September results had me almost at the point where I could stop taking bactrim, but not yet. More importantly, the majority of my immunizations were still in effect. The only ones missing were measles and rubella. However, I was instructed to wait before getting reimmunized. The MMR (measles, mumps, rubella) vaccine uses live but weakened viruses. A weak enough immune system, however, would not mount a sufficient response, which would lead to actual illness. I had repeat tests in December, and this time, the results were good enough for me to stop taking bactrim and get my MMR shot, which I did in January after the holidays. And just in the nick of time, as it was shortly thereafter that the California measles outbreak was all over the headlines.

I was generally able to keep any worry about catching an illness like measles in the back of my mind, but that didn't mean it wasn't there, especially when I had to travel to highly populated areas. And with a weakened immune system, the results would not have been pretty. Before my cancer experience, I didn't think all that much about the rise in parents who do not vaccinate their children beyond expressions of puzzlement every now and then, but now, the thought of future cancer patients being at heightened risks of hitting roadblocks or even losing their fights due to preventable illnesses I find very worrisome. Same goes for taking chances with having your children catch these diseases. What enabled the spread of the recent measles outbreak was a critical mass of unvaccinated individuals. Modern day residents of developed countries are privileged to be able to grow up without worrying about illnesses that used to claim many, many people in their youth. Most young parents today haven't had these illnesses, and quite possibly their parents haven't either. So with these diseases seen more and more as parts of history rather than ailments with tangible effects that caused loved ones to suffer, it becomes easier to question preventative measures such as vaccines. I'm going to say it here, as someone who's gone through a nasty illness young: if there were a vaccine for what I had, I sure would have liked to have had it.