CXCL9 and COVID-19: Linear regression revealed a trend toward an association between the number of COVID-19 vaccine doses, the neutralizing capacity of IgG against SARS-CoV-2, the titers of IgG against SARS-CoV-2 S1 protein, and plasma levels of CXCL9, CCL23, prothrombin, and CRP with the development and/or persistence of LC, compared to healthy donors.