Arthritis flare-up; Interchange of vaccine products; Revaccination with different COVID-19 vaccine; This spontaneous case was reported by a patient family member or friend and describes the occurrence of ARTHRITIS (Arthritis flare-up), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine) in a female patient of an unknown age who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.     Previously administered products included for Product used for unknown indication: Pfizer (Dose 2, She flared with Pfizer.), Pfizer (Dose 1 and She flared with Pfizer.). Past adverse reactions to the above products included Vaccination adverse reaction with Pfizer and Pfizer. Concurrent medical conditions included Arthritis and IBD.    On an unknown date, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced ARTHRITIS (Arthritis flare-up), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine). At the time of the report, ARTHRITIS (Arthritis flare-up), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine) outcome was unknown.            No concomitant medications were reported.  No treatment details 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 is a spontaneous case concerning a female patient of unknown age with medical history of arthritis, who experienced the unexpected, non-serious adverse event of special interest of Arthritis (Arthritis flare-up), after receiving a dose of mRNA-1273 vaccine (reported as third COVID-19 vaccine). Exact date of vaccination, onset date of the event, clinical course, diagnostic tests and treatment details were not provided in the case. The outcome of the event was unknown at the time of the report. Medical history of arthritis remains a risk factor for the event. Revaccination with different COVID-19 vaccine and Interchange of vaccine products were also reported as additional events. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a female patient of unknown age with medical history of arthritis, who experienced the unexpected, non-serious adverse event of special interest of Arthritis (Arthritis flare-up), after receiving a dose of mRNA-1273 vaccine (reported as third COVID-19 vaccine). Exact date of vaccination, onset date of the event, clinical course, diagnostic tests and treatment details were not provided in the case. The outcome of the event was unknown at the time of the report. Medical history of arthritis remains a risk factor for the event. Revaccination with different COVID-19 vaccine and Interchange of vaccine products were also reported as additional events. The benefit-risk relationship of mRNA-1273 is not affected by this report.