However, a recent study examining immunological predictors of impaired immune response to SARS-CoV-2 vaccination found no association to central memory CD4+ or CD8+ T cells, but a significantly higher frequency of effector memory CD8+ T cells in those of impaired humoral immune response [36], and a similar trend has also been observed with humoral response to influenzae vaccination in CVID patients [55]. This evidence concerns the gene CD4 and common variable immunodeficiency.