Recent diagnosis of COVID-19; Graves disease/ TSH was Elevated or Her tests continue to show an elevated T3 and TSH; Likely graves disease with benign appearing nodules; This spontaneous case was reported by a patient and describes the occurrence of BASEDOW'S DISEASE (Graves disease/ TSH was Elevated or Her tests continue to show an elevated T3 and TSH) in a 71-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 013M20A, 038A21A and 058H21A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 14-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 14-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 30-Nov-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 19-Apr-2022, the patient experienced BASEDOW'S DISEASE (Graves disease/ TSH was Elevated or Her tests continue to show an elevated T3 and TSH) (seriousness criterion medically significant) and THYROID MASS (Likely graves disease with benign appearing nodules). On an unknown date, the patient experienced COVID-19 (Recent diagnosis of COVID-19). The patient was treated with LEVOTHYROXINE SODIUM (SYNTHROID) ongoing since an unknown date at an unspecified dose and frequency. At the time of the report, BASEDOW'S DISEASE (Graves disease/ TSH was Elevated or Her tests continue to show an elevated T3 and TSH), THYROID MASS (Likely graves disease with benign appearing nodules) and COVID-19 (Recent diagnosis of COVID-19) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2021, Blood test: TSH elevated. On 19-Apr-2022, Ultrasound scan: Showed likely graves disease with benign appearing nodules.. On 04-Oct-2022, Blood thyroid stimulating hormone: 4.520. On an unknown date, Blood thyroid stimulating hormone: Elevated and 4.270. On an unknown date, SARS-CoV-2 test: Positive. On an unknown date, Tri-iodothyronine: Elevated.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Concomitant medication was not provided. Patient had received routine blood tests for every 3 months.  Company Comment This spontaneous case concerns a 71-years-old female patient, with  no medical history reported who experienced the unexpected seriousness criterion medically significant event  of Basedow disease and the unexpected event of Covid-19 in the context of  3rd.  dose of  mRNA-1273 vaccine.  The first 2 doses were administrated with moderna vaccine in an appropriate schedule. The serious event occurred approximately 5 months after the 3rd. dose and Covid-19 event  on unknown date but before it. The benefit-risk relationship of mrna-1273 vaccine is not affected by this report. Events seriousness was assessed based on medical judgement.   Most recent FOLLOW-UP information incorporated above includes: On 25-Oct-2022: Follow-up received and added batch no. for third dose.; Sender's Comments: Company Comment This spontaneous case concerns a 71-years-old female patient, with  no medical history reported who experienced the unexpected seriousness criterion medically significant event  of  Basedow disease and the unexpected event of Covid-19 in the context of  3rd.  dose of  mRNA-1273 vaccine.  The first 2 doses were administrated with moderna vaccine in an appropriate schedule. The serious event occurred approximately 5 months after the 3rd. dose and Covid-19 event  on unknown date but before it. The benefit-risk relationship of mrna-1273 vaccine is not affected by this report. Events seriousness was assessed based on medical judgement.