Considering the genetic heterogeneity in different ethnic groups, larger cohorts across different geographies and ethnicities, together with functional studies, should be conducted to obtain conclusive evidence of the association between the HLA/KIR interaction system in the immune response and disease progression of COVID-19 and to dissect the role of CTL- and NK cell-mediated killing in the process of SARS-CoV-2 infection and replication. This evidence concerns the gene KIR3DL1 and COVID-19.