CD4 and COVID-19: HIV infection is an independent risk factor for both severe COVID-19 at admission and in-hospital mortality [3], and it is associated with a higher risk of severe disease due to SARS-CoV-2 infection [4], impaired immunity (low CD4+ cell number defined both as <200 cells/mm3 and as <350 cells/mm3) [5], CD4 + T-cell count nadir <200 cells mm3 [6] and the coexistence of comorbidities known as risk factors (i.e., diabetes and cardiovascular diseases), which are frequently diagnosed in HIV-positive patients [7] and are all factors involved.