In the study by Dan et al. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined over time with a half-life 3 to 5 months, and the majority of SARS-CoV-2-specific memory CD8+ T cells were terminally differentiated effector memory cells (CD45RA+CCR7-), with small populations of central memory (CD45RA-CCR7+) and effector memory (CD45RA-CCR7-), while a plurality of the SARS-CoV-2 memory CD4+ T cells present at ≥ 6 months after infection had a CD45RA-CCR7+ central memory phenotype [15]. This evidence concerns the gene CCR7 and infection.