The specific classical monocyte population we identified in this study is characterized by high expression of CXCL8, CTSL, CXCL2, and CCL2, all of which are molecules associated with rheumatic disease activity, and we hypothesized that the COVID-19 vaccination may have been the trigger for the rheumatic activity in our patients. The gene discussed is CXCL2; the disease is COVID-19.