If you have undergone chemotherapy, biological therapy, and/or stem cell transplantation it is likely that you have a weakened immune system characterized by the lower levels of white blood cells (neutrophils) and antibodies (biological markers used by the immune system to identify foreign objects). After lymphoma treatment ends, your white blood cells and antibodies should start to recover. But this process may take many months. In the meantime, you may be susceptible to infections, particularly from viruses.
Some viruses in our bodies that normally stay inactive may often become active once lymphoma treatment is finished. For example, the reactivation of the herpes zoster virus (the virus that causes chicken pox) can cause shingles, which is known for its characteristic symptoms of painful blisters around the side of your torso. Symptoms may be worse in those who have a weakened immune system. Hepatitis B is another virus that has been noted to reactivate upon lymphoma treatment. In any case, seek help from your doctor at any early signs of a viral infection, early treatment from antiviral drugs may help alleviate your symptoms.
Lymphoma Association. Late effects of lymphoma treatment