As the increase in Treg proportions with increased FOXP3 levels was also associated with poor outcomes in SARS-CoV-2 infections [35], we investigated whether CLL patients with higher aTreg percentages among FOXP3+CD4+ T cells at the start of follow-up would experience a more severe disease course with infectious complications requiring hospitalisation using the approach described before [36,37]. Here, CD4 is linked to B-cell chronic lymphocytic leukemia.