Reactive arthritis; Bilateral tendinitis on her wrists; Bladder issues; Other pains and aches; GI virus came back or had never gone away, and it was reactivated after the vaccine; This spontaneous case was reported by an other health care professional and describes the occurrence of ARTHRITIS REACTIVE (Reactive arthritis) in a 46-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 012L20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included GI infection, Viral myocarditis (Because of Virus she had) in June 2020 and Cardiomyopathy in June 2020. Concurrent medical conditions included Sleep disorder. Concomitant products included HYDROXYCHLOROQUINE, LEVOTHYROXINE SODIUM (SYNTHROID), COLECALCIFEROL (VITAMIN D [COLECALCIFEROL]), FAMOTIDINE, CYANOCOBALAMIN (B12 [CYANOCOBALAMIN]) and FISH OIL for an unknown indication.    On 20-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 20-Jan-2021, the patient experienced GASTROINTESTINAL VIRAL INFECTION (GI virus came back or had never gone away, and it was reactivated after the vaccine), BLADDER DISORDER (Bladder issues) and PAIN (Other pains and aches). On 27-Jan-2021, the patient experienced ARTHRITIS REACTIVE (Reactive arthritis) (seriousness criterion medically significant) and TENDONITIS (Bilateral tendinitis on her wrists). The patient was treated with HYDROXYCHLOROQUINE SULFATE (PLAQUENIL [HYDROXYCHLOROQUINE SULFATE]) for Tendinitis, at an unspecified dose and frequency; SULFASALAZINE in March 2021 for Tendinitis, at an unspecified dose and frequency and Immunotherapy (Immunosupressant) for Arthritis reactive. At the time of the report, ARTHRITIS REACTIVE (Reactive arthritis), TENDONITIS (Bilateral tendinitis on her wrists), BLADDER DISORDER (Bladder issues) and PAIN (Other pains and aches) outcome was unknown and GASTROINTESTINAL VIRAL INFECTION (GI virus came back or had never gone away, and it was reactivated after the vaccine) had not resolved.        mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosing remained unchanged.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Concomitant medication use information was  provided by reporter that includes Medication for sleep disorder.   The reporter reported that patient was on Plaquenil before, and they changed it to Sulfasalazine in March because the tendinitis wouldn't go away. And also the rheumatologist put her on immunosuppressants.  Company comment: This case concerns a  46-year-old, female patient with medical history of GI virus, Cardiomyopathy, and viral myocarditis, who experienced the unexpected events of decreased Arthritis reactive, GI viral infection, Tendonitis, Bladder disorder and pain. The events occurred same day after the first dose. The rechallenge was unknown since no information is based on the first dose. The reporter assessed the events as related to the product. The benefit-risk relationship is not affected by this report.   This case was linked to MOD-2021-331261 (Patient Link).; Sender's Comments: This case concerns a  46-year-old, female patient with medical history of GI virus, Cardiomyopathy, and viral myocarditis, who experienced the unexpected events of decreased Arthritis reactive, GI viral infection, Tendonitis, Bladder disorder and pain. The events occurred same day after the first dose. The rechallenge was unknown since no information is based on the first dose. The reporter assessed the events as related to the product. The benefit-risk relationship is not affected by this report.