My heart's been fluttering; I'm really sick; Pain in the arm; Couldn't even move it (the arm); Fast heart beat; Thought I was gonna die for the pain in my chest; thought I was gonna die for the pain in my chest; No energy or so ever; Fatigue; This spontaneous case was reported by a consumer and describes the occurrence of CARDIAC FLUTTER (My heart's been fluttering) in a 67-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 017E21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 19-Sep-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 19-Sep-2021, the patient experienced CARDIAC FLUTTER (My heart's been fluttering) (seriousness criterion medically significant), ILLNESS (I'm really sick), PAIN IN EXTREMITY (Pain in the arm), MOBILITY DECREASED (Couldn't even move it (the arm)), HEART RATE INCREASED (Fast heart beat), CHEST PAIN (Thought I was gonna die for the pain in my chest), FEELING ABNORMAL (thought I was gonna die for the pain in my chest), ASTHENIA (No energy or so ever) and FATIGUE (Fatigue). At the time of the report, CARDIAC FLUTTER (My heart's been fluttering), ILLNESS (I'm really sick), PAIN IN EXTREMITY (Pain in the arm), MOBILITY DECREASED (Couldn't even move it (the arm)), HEART RATE INCREASED (Fast heart beat), CHEST PAIN (Thought I was gonna die for the pain in my chest), FEELING ABNORMAL (thought I was gonna die for the pain in my chest), ASTHENIA (No energy or so ever) and FATIGUE (Fatigue) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 19-Sep-2021, Heart rate: fast (High) fast.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.       Concomitant product use was not provided by the reporter.  No treatment information was provided.  Company Comment: This case concerns a  67-year-old, male patient with no relevant medical history, who experienced the unexpected events of cardiac flutter, illness, pain in extremity, mobility decreased, heart rate increased, chest pain, feeling abnormal and asthenia, also expected event of fatigue. The events occurred approximately 1 day after the first dose of Spikevax. The rechallenge was unknown since no information about the second dose was disclosed. The benefit-risk relationship of Spikevax is not affected by this report. Event seriousness assessed as per Regulatory Authority reporting, however there was no information in the source document supporting that the events resulted in a persistent or permanent incapacity; Sender's Comments: This case concerns a  67-year-old, male patient with no relevant medical history, who experienced the unexpected events of cardiac flutter, illness, pain in extremity, mobility decreased, heart rate increased, chest pain, feeling abnormal and asthenia, also expected event of fatigue. The events occurred approximately 1 day after the first dose of Spikevax. The rechallenge was unknown since no information about the second dose was disclosed. The benefit-risk relationship of Spikevax is not affected by this report. Event seriousness assessed as per Regulatory Authority reporting, however there was no information in the source document supporting that the events resulted in a persistent or permanent incapacity