[after the second dose] it triggered rheumatoid arthritis in both my hands; my immune system went crazy; it was seeking my red blood cells and destroying them; I couldn't chew; couldn't get to my room without a walker; I had pain in my legs, toes, jaw, it was so bad; they were so swollen; I had pain in my legs, toes, jaw, it was so bad; couldn't move my hands; This spontaneous case was reported by a consumer and describes the occurrence of RHEUMATOID ARTHRITIS ([after the second dose] it triggered rheumatoid arthritis in both my hands) and IMMUNE SYSTEM DISORDER (my immune system went crazy) in a 101-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 001A21A and 042L20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 23-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 26-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In February 2021, the patient experienced RHEUMATOID ARTHRITIS ([after the second dose] it triggered rheumatoid arthritis in both my hands) (seriousness criterion medically significant), IMMUNE SYSTEM DISORDER (my immune system went crazy) (seriousness criterion medically significant), RED BLOOD CELL ABNORMALITY (it was seeking my red blood cells and destroying them), MASTICATION DISORDER (I couldn't chew), GAIT DISTURBANCE (couldn't get to my room without a walker), PAIN IN EXTREMITY (I had pain in my legs, toes, jaw, it was so bad), SWELLING (they were so swollen), PAIN IN JAW (I had pain in my legs, toes, jaw, it was so bad) and MOBILITY DECREASED (couldn't move my hands). The patient was treated with TURMERIC [CURCUMA LONGA RHIZOME] in February 2021 for Adverse event, at a dose of 4-5 times a day and PARACETAMOL (TYLENOL) for Arthritic pains, at an unspecified dose and frequency. At the time of the report, RHEUMATOID ARTHRITIS ([after the second dose] it triggered rheumatoid arthritis in both my hands), IMMUNE SYSTEM DISORDER (my immune system went crazy), RED BLOOD CELL ABNORMALITY (it was seeking my red blood cells and destroying them), MASTICATION DISORDER (I couldn't chew), GAIT DISTURBANCE (couldn't get to my room without a walker), PAIN IN EXTREMITY (I had pain in my legs, toes, jaw, it was so bad), SWELLING (they were so swollen), PAIN IN JAW (I had pain in my legs, toes, jaw, it was so bad) and MOBILITY DECREASED (couldn't move my hands) outcome was unknown.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Treatment also includes prednisone 10 mg, reduced to 5 mg for 30 days, then prednisone 2.5 mg for 30 days, and now prednisone 2.5mg every other day.  Company comment: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded. However, patient´s age (101 years) could probably be a contributory factor to the events.   This case was linked to MOD-2021-297603 (Patient Link).; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded. However, patient´s age (101 years) could probably be a contributory factor to the events.