fluttering heart; leg started to swelled; shortness of breath; This spontaneous case was reported by a consumer and describes the occurrence of CARDIAC FLUTTER (fluttering heart) in a 65-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 939904, 031L20A. and 011J20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included Pulmonary embolism.   On 12-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 09-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 26-Oct-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 29-Oct-2021, the patient experienced CARDIAC FLUTTER (fluttering heart) (seriousness criterion medically significant), PERIPHERAL SWELLING (leg started to swelled) and DYSPNOEA (shortness of breath). The patient was treated with APIXABAN (ELIQUIS) at an unspecified dose and frequency and DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) at an unspecified dose and frequency. At the time of the report, CARDIAC FLUTTER (fluttering heart), PERIPHERAL SWELLING (leg started to swelled) and DYSPNOEA (shortness of breath) had not resolved.            Concomitant medication was not provided by the reporter.   Patient went to the ER were they checked for blood clots and did not find blood clot, also  performed an ultrasound and since the patient is allergic to the contrast chemical was indicated  Benadryl and steroids.  Patient has no previous heart conditions nor has had covid-19.  Patient had inquired if symptoms are common and whether it would prevent from getting. another Moderna vaccine in the future. Company comment: This case concerns a 65-year-old, female patient with medical history of pulmonary embolism, who experienced the unexpected event cardiac flutter and non serious events of peripheral swelling and dyspnoea. The event of cardiac flutter (described as fluttering heart) occurred approximately 3 days after the third dose of mRNA-1273. Very limited information was provided regarding diagnostic findings. The rechallenge was not applicable as events occurred after third dose and no further dosing was reported or planned, based on information provided. The above mentioned medical history remains a confounder. The benefit-risk relationship of mRNA-1273 is not affected by this report.   This case was linked to MOD-2021-400069 (Patient Link).; Sender's Comments: This case concerns a 65-year-old, female patient with medical history of pulmonary embolism, who experienced the unexpected event cardiac flutter and non serious events of peripheral swelling and dyspnoea. The event of cardiac flutter (described as fluttering heart) occurred approximately 3 days after the third dose of mRNA-1273. Very limited information was provided regarding diagnostic findings. The rechallenge was not applicable as events occurred after third dose and no further dosing was reported or planned, based on information provided. The above mentioned medical history remains a confounder. The benefit-risk relationship of mRNA-1273 is not affected by this report.