PTPN22 and rheumatoid arthritis: <b>Purpose of the research.</b> To investigate the differences in the expression of the Protein tyrosine phosphatase non-receptor type 22 (PTPN22), Tumor necrosis factor receptor-associated factor 1 (TRAF-1) and Interleukin-1 beta (IL-1β) genes in patients with rheumatoid arthritis (RA) and healthy controls following SARS-CoV-2 infection or vaccination.