CCR9 and COVID-19: This study indicated that solute carrier family 6 member 20 gene (SLC6A20), LZTFL1, C-C chemokine receptor type 9 gene (CCR9), FYVE and coiled-coil domain autophagy adaptor 1 gene (FYCO1), C-X-C chemokine receptor type 6 gene (CXCR6), X-C Motif Chemokine Receptor 1 gene (XCR1), and ABO genes were involved in severity of COVID-19 [10].