experienced fever and chills; experienced fever and chills; fluttering heart; One or two days after the injection, her husband started to experience shortness of breath; fast-beating; fatigue; This spontaneous case was reported by a patient family member or friend and describes the occurrence of CARDIAC FLUTTER (fluttering heart) in a 57-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Patient had no allergies. Patient had no acute or chronic illnesses at the time of vaccination. Patient was not vaccinated with any other manufacturer vaccine one month prior. Patient did not have history of myopericarditis or pericarditis.  The patient's past medical history included Muscle injury (had an injury in a muscle of chest because lifted something heavy at work.) and COVID-19 (3 to 4 weeks before first dose and was not hospitalized.) in 2022.    On 24-Jun-2022, the patient received first dose of mRNA-1273 (Spikevax) (Intramuscular) 1 dosage form. In June 2022, the patient experienced CARDIAC FLUTTER (fluttering heart) (seriousness criterion medically significant), DYSPNOEA (One or two days after the injection, her husband started to experience shortness of breath), PALPITATIONS (fast-beating) and FATIGUE (fatigue). On 28-Jun-2022, the patient experienced PYREXIA (experienced fever and chills) and CHILLS (experienced fever and chills). The patient was treated with ACETYLSALICYLIC ACID (ALKA-SELTZER) at an unspecified dose and frequency and GUAIFENESIN (MUCINEX) at an unspecified dose and frequency. At the time of the report, CARDIAC FLUTTER (fluttering heart), DYSPNOEA (One or two days after the injection, her husband started to experience shortness of breath), PALPITATIONS (fast-beating), FATIGUE (fatigue), PYREXIA (experienced fever and chills) and CHILLS (experienced fever and chills) had not resolved.        The action taken with mRNA-1273 (Spikevax) (Intramuscular) was unknown.       Concomitant medications were not provided.  The reporter stated that the patient had a chest muscle injury because of lifting something heavy at work, which the reporter thought to have triggered the chest symptoms but reporter was not sure of that.  It was reported that no lab tests were done.  No COVID-19 test was performed and patient was not hospitalized.  The reporter stated that there is no history of Myocarditis/pericarditis.  Company Comment: This spontaneous case concerns a 57-year-old, male patient with no relevant medical history reported, who experienced the unexpected, serious (medically significant) AESI of cardiac flutter, and other associated unexpected and expected, non-serious events. The events occurred beginning 1 or 2 days and up to 4 days after receiving the first dose of the mRNA-1273 vaccine. It was reported that 1 or 2 days after vaccination, the patient started to experience shortness of breath, 'fluttering heart', 'fast-beating' and fatigue. Four days after vaccination, the patient experienced fever and chills. The patient took Alka-Seltzer and Mucinex (unspecified dose, frequency and duration) as treatment. It was also reported that the patient will seek Emergency Room consultation, however, no details were provided at the time of the report. The events had not resolved at the time of the report. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This spontaneous case concerns a 57-year-old, male patient with no relevant medical history reported, who experienced the unexpected, serious (medically significant) AESI of cardiac flutter, and other associated unexpected and expected, non-serious events. The events occurred beginning 1 or 2 days and up to 4 days after receiving the first dose of the mRNA-1273 vaccine. It was reported that 1 or 2 days after vaccination, the patient started to experience shortness of breath, 'fluttering heart', 'fast-beating' and fatigue. Four days after vaccination, the patient experienced fever and chills. The patient took Alka-Seltzer and Mucinex (unspecified dose, frequency and duration) as treatment. It was also reported that the patient will seek Emergency Room consultation, however, no details were provided at the time of the report. The events had not resolved at the time of the report. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.