extreme flare up of her rheumatoid arthritis; chills; swollen lymph nodes under her arm; breasts were also engorged; every joint was painful (shoulders, bilateral hip).; This spontaneous case was reported by a patient and describes the occurrence of RHEUMATOID ARTHRITIS (extreme flare up of her rheumatoid arthritis), CHILLS (chills), LYMPHADENOPATHY (swollen lymph nodes under her arm), BREAST ENGORGEMENT (breasts were also engorged) and ARTHRALGIA (every joint was painful (shoulders, bilateral hip).) in a 47-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 026B21A, 042L20A and 025J20-2A) for COVID-19 vaccination.     The patient's past medical history included Rheumatoid arthritis, Hashimoto's disease and Thyroidectomy.   On 28-Dec-2020, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 27-Jan-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 21-Aug-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On an unknown date, the patient experienced RHEUMATOID ARTHRITIS (extreme flare up of her rheumatoid arthritis) (seriousness criteria disability and medically significant), CHILLS (chills) (seriousness criterion disability), LYMPHADENOPATHY (swollen lymph nodes under her arm) (seriousness criterion disability), BREAST ENGORGEMENT (breasts were also engorged) (seriousness criterion disability) and ARTHRALGIA (every joint was painful (shoulders, bilateral hip).) (seriousness criterion disability). The patient was treated with HYDROCORTISONE at an unspecified dose and frequency; ADALIMUMAB (HUMIRA) at an unspecified dose and frequency; ETANERCEPT (ENBREL) at an unspecified dose and frequency and HYDROCODONE at an unspecified dose and frequency. At the time of the report, RHEUMATOID ARTHRITIS (extreme flare up of her rheumatoid arthritis), CHILLS (chills), LYMPHADENOPATHY (swollen lymph nodes under her arm), BREAST ENGORGEMENT (breasts were also engorged) and ARTHRALGIA (every joint was painful (shoulders, bilateral hip).) outcome was unknown.            No concomitant medication information was mentioned by reporter. Treatment medication use information was provided by reporter that includes oral steroids.  Company comment: This case concerns a 47-year-old, female patient with relevant medical history of Rheumatoid arthritis, Hashimoto's disease and Thyroidectomy, who experienced the unexpected events of Rheumatoid arthritis, Breast engorgement and the expected event of Chills, Lymphadenopathy and Arthralgia. The events occurred on an unknown date after the dose of Moderna vaccine. The rechallenge was unknown as the events occurred on an unknown date. The events were considered related to the product per the reporter's assessment. The events of Chills, Lymphadenopathy and Arthralgia are consistent with the current understanding of the mechanism of action of the vaccine. The benefit-risk relationship of Moderna Covid-19 vaccine is not affected by this report.   This case was linked to MOD-2021-336827, MOD-2021-336699 (Patient Link).; Sender's Comments: This case concerns a 47-year-old, female patient with relevant medical history of Rheumatoid arthritis, Hashimoto's disease and Thyroidectomy, who experienced the unexpected events of Rheumatoid arthritis, Breast engorgement and the expected event of Chills, Lymphadenopathy and Arthralgia. The events occurred on an unknown date after the dose of Moderna vaccine. The rechallenge was unknown as the events occurred on an unknown date. The events were considered related to the product per the reporter's assessment. The events of Chills, Lymphadenopathy and Arthralgia are consistent with the current understanding of the mechanism of action of the vaccine. The benefit-risk relationship of Moderna Covid-19 vaccine is not affected by this report.