CD4 and HIV infectious disease: In addition, since the majority of data from clinical trials refer to PLWH with good CD4+ T-cell counts, which are sometimes comparable to those of individuals with no HIV infection, the protection period provided by vaccination to PLWH with CD4+ T-cell counts < 200 cells/μL might be shorter than that observed in subjects with CD4+ T-cell counts > 500 cells/μL, and therefore the vaccination should be carried out at shorter intervals.