CD4 and herpes zoster: Zoster infection drives the expansion of specific CD4+ T lymphocyte population and this fact explains the lower incidence of reinfection in the period after the first event.5 Besides advanced age, other well-known conditions that compromise cell-mediated immunity and comprise risk factors for herpes zoster are bone marrow or solid organ transplantation, lymphoproliferative diseases, leukemia and human immunodeficiency virus (HIV) infection.