CD8A and viral infectious disease: The selection of these two indicators was based on the following: T cells are the core components of anti-varicella zoster virus (VZV) immunity, peripheral blood CD4+/CD8+ ratio reflects the dynamic balance between helper T cells and cytotoxic T cells, and a decrease in the ratio may indicate an insufficient anti-viral immune response; A higher proportion of Treg cells may exacerbate persistent viral infection by inhibiting the immune response.