XCL1 and COVID-19: In light of the new findings about exclusive highly clonally expanded SARS-CoV-2-specific CD8+ T cells with preferentially expressed tissue-resident genes (XCL1, CXCR6, and ITGAE) in the BAL of moderate COVID-19 cases (57) and not in the critical/severe COVID-19 patients, induction of SARS-CoV-2 specific CD8+ T cells that home to airway epithelium emphasizes the importance of developing vaccination strategies that induce TRM antigen-specific CD8+ T cells that will improve efficacy of vaccination against respiratory pathogens including SARS-CoV-2.