In Japan, where serum IFN-λ3 has been commercially used to asses COVID-19 progression, Sekimoto et al. [16] showed that patients negative for both IFN-λ3 and chemokine (C-C motif) ligand 17 (CCL17) did not experience disease progression, whereas elevated IFN-λ levels heralded the advancement of COVID-19 [16]. This evidence concerns the gene CCL17 and COVID-19.