ABSTRACT
We herein report a 60-year-old woman who experienced severe flare of rheumatoid arthritis (RA) and Epstein-Barr virus (EBV) positivity following administration of the messenger ribonucleic acid (mRNA)-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. Since 40 years old, she had been in long-term remission of anti-citrullinated protein antibody-positive RA. Ten days after SARS-CoV-2 vaccination, she presented with a high fever and polyarthritis, active synovitis on joint ultrasound, a clinical disease activity index of 35, and positivity for anti-early antigen, diffuse type and restricted type (EA DR) IgG and EBV deoxyribonucleic acid (EBV-DNA). Tocilizumab was introduced to treat RA. The RA disease activity disappeared, and anti-EA DR IgG and EBV-DNA became negative.