Heart flutters; Regular premature ventricular contractions; Difficulty breathing/ shortness of breath; chest tightness/ weight on the chest/ Pressure in the chest; Heart palpitations; Anxiety; Cough; Cannot go upstairs; fatigue; Patient is breast feeding; This spontaneous case was reported by a consumer and describes the occurrence of CARDIAC FLUTTER (Heart flutters) and VENTRICULAR EXTRASYSTOLES (Regular premature ventricular contractions) in a 30-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 038C21A, 019A21A and 010A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.    Co-suspect product included non-company product INFLUENZA VACCINE RHA 3V (BACULOVIRUS) (FLUBLOK) for an unknown indication.    Concurrent medical conditions included Graves' disease (the patient has graves' disease (autoimmune) and had it even before the first dose of the moderna vaccine) since 01-Oct-2016. Concomitant products included PROGESTERONE (PROGESTIN) from 01-May-2021 to an unknown date for Breast feeding, THIAMAZOLE (TAPAZOLE) from 01-Oct-2016 to an unknown date for Graves' disease, SERTRALINE from 01-Apr-2021 to an unknown date for an unknown indication.   On 10-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 07-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 22-Oct-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 22-Oct-2021, the patient started INFLUENZA VACCINE RHA 3V (BACULOVIRUS) (FLUBLOK) (unknown route) 1 dosage form. On 10-Mar-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced MATERNAL EXPOSURE DURING BREAST FEEDING (Patient is breast feeding). On 30-Oct-2021, the patient experienced CARDIAC FLUTTER (Heart flutters) (seriousness criterion medically significant), VENTRICULAR EXTRASYSTOLES (Regular premature ventricular contractions) (seriousness criterion medically significant), DYSPNOEA (Difficulty breathing/ shortness of breath), CHEST DISCOMFORT (chest tightness/ weight on the chest/ Pressure in the chest), PALPITATIONS (Heart palpitations), ANXIETY (Anxiety), COUGH (Cough), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (Cannot go upstairs) and FATIGUE (fatigue). On 10-Mar-2021, MATERNAL EXPOSURE DURING BREAST FEEDING (Patient is breast feeding) had resolved. At the time of the report, CARDIAC FLUTTER (Heart flutters), VENTRICULAR EXTRASYSTOLES (Regular premature ventricular contractions), DYSPNOEA (Difficulty breathing/ shortness of breath), CHEST DISCOMFORT (chest tightness/ weight on the chest/ Pressure in the chest), PALPITATIONS (Heart palpitations), ANXIETY (Anxiety), COUGH (Cough), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (Cannot go upstairs) and FATIGUE (fatigue) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 31-Oct-2021, Chest X-ray: normal (normal) No radiographic evidence of acute cardiopulmonary disease. On 31-Oct-2021, Echocardiogram: normal (normal) 1. Left ventricular systolic function is normal. The LVEF is 65 %(+- 3%). 2. Normal diastolic pattern with normal left atrial pressure. 3. There are no segmental wall motion abnormalities. 4. Normal right ventricular size and systolic function. 5. No significant valvular abnormalities. 6. No pericardial effusion is seen. 7. There are no prior studies available for comparison.. On 09-Nov-2021, Full blood count: normal (normal) normal. On 09-Nov-2021, Vital signs measurement: normal (normal) normal. On an unknown date, Echocardiogram: normal (normal) Echo was normal. On an unknown date, Electrocardiogram: regular (normal) EKG was done and showed regular premature ventricular contraction.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter considered VENTRICULAR EXTRASYSTOLES (Regular premature ventricular contractions), DYSPNOEA (Difficulty breathing/ shortness of breath), CHEST DISCOMFORT (chest tightness/ weight on the chest/ Pressure in the chest), PALPITATIONS (Heart palpitations), ANXIETY (Anxiety), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (Cannot go upstairs) and MATERNAL EXPOSURE DURING BREAST FEEDING (Patient is breast feeding) to be possibly related. No further causality assessments were provided for CARDIAC FLUTTER (Heart flutters), COUGH (Cough) and FATIGUE (fatigue).    No treatment information was reported.  The patient was sent to the ER and repeated the EKG and ran full CBC panel, ran electrolytes, and ran thyroid labs as the patient has graves' disease (autoimmune) and had it even before the first dose of the moderna vaccine.  The patient stated that she was not diagnosed with myocarditis and stated that they do not know what is causing this and said it could be due to the vaccine but were not sure.  The patient was told that she can only get a "holter" monitor on 02Dec2021 and stated that she cannot go upstairs and cannot carry her daughter who is an infant.  There is no any history of Myocarditis/pericarditis.  Patient also experienced  events Went to urgent care, Went to the ER , Due to the vaccine,  Symptoms are continuing,  Symptoms today are worse,   Gets better somedays,  Are worse somedays, Cannot carry her infant daughter  Company comment: This case concerns a 31 year old female patient with medical history of Graves disease who experienced serious unexpected AESI of cardiac flutter (ventricular extrasystoles) after booster dose of mRNA-1273. The events occurred 9 days after vaccination. The re-challenge is not applicable.  Patient´s medical history and co-suspect flu vaccine remains confounders in this case. The benefit-risk relationship of mRNA-1273 is not affected by this report. This case was upgraded due to medical judgment because of the nature of the event, the temporal relationship and the need for further studies to clarify.   This case was linked to MOD-2021-375455 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 08-Nov-2021: Significant follow-up received on 08-NOV- 2021,  Events added, Lab reports added On 08-Nov-2021: Significant follow up received on 08 -NOV-2021, event i lost 13 lbs (weight decreased ) was nullified.; Sender's Comments: This case concerns a 31 year old female patient with medical history of Graves disease who experienced serious unexpected AESI of cardiac flutter (ventricular extrasystoles) after booster dose of mRNA-1273. The events occurred 9 days after vaccination. The re-challenge is not applicable.  Patient´s medical history and co-suspect flu vaccine remains confounders in this case. The benefit-risk relationship of mRNA-1273 is not affected by this report. This case was upgraded due to medical judgment because of the nature of the event, the temporal relationship and the need for further studies to clarify.