This spontaneous case was reported by a consumer and describes the occurrence of RHEUMATOID ARTHRITIS (Rheumatoid arthritis flare up) in an adult female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. Co-suspect product included non-company product UPADACITINIB (RINVOQ) for Rheumatoid arthritis. Concurrent medical conditions included Rheumatoid arthritis. In February 2021, the patient received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. In March 2021, received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient started UPADACITINIB (RINVOQ) (Oral) Unknown. On an unknown date, the patient experienced RHEUMATOID ARTHRITIS (Rheumatoid arthritis flare up) (seriousness criterion medically significant), PAIN (weather related pain and swelling), SWELLING (weather related pain and swelling) and VACCINATION SITE PAIN (Sore arm after vaccines). At the time of the report, RHEUMATOID ARTHRITIS (Rheumatoid arthritis flare up), PAIN (weather related pain and swelling), SWELLING (weather related pain and swelling) and VACCINATION SITE PAIN (Sore arm after vaccines) outcome was unknown. No concomitant medications were reported. It was unknown if patient was enrolled in a COVID-19 Vaccine Trial. The reporter's causality for the events of vaccination site pain, pain, swelling and rheumatoid arthritis was not provided with RINVOQ (UPADACITINIB). No treatment medications were reported. This case was identified as part of a retrospective clean-up activity where certain emails received in the Moderna mailbox were missed to be booked-in. Company Comment: This spontaneous case concerns an adult female patient with concurrent Rheumatoid arthritis, who experienced the unexpected, serious  (medically significant) adverse event of special interest Rheumatoid arthritis (Rheumatoid arthritis flare up) on an unknown date in the context of receiving a dose of mRNA-1273 vaccine. Onset latency could not be established as dates of vaccination and date of event onset were not provided. Patient received a 2-dose primary series of mRNA-1273 vaccine on unknown dates and interval. The concurrent Rheumatoid arthritis remains a confounder as the disease itself is known to result in flares. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. Sender's Comments: This spontaneous case concerns an adult female patient with concurrent Rheumatoid arthritis, who experienced the unexpected, serious (medically significant) adverse event of special interest Rheumatoid arthritis (Rheumatoid arthritis flare up) on an unknown date in the context of receiving a dose of mRNA-1273 vaccine. Onset latency could not be established as dates of vaccination and date of event onset were not provided. Patient received a 2-dose primary series of mRNA-1273 vaccine on unknown dates and interval. The concurrent Rheumatoid arthritis remains a confounder as the disease itself is known to result in flares. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.