ARTRIAL FLUTTER (HEART RATE HIGH, HEART PALPITATIONS, FELT FAINTING, DIZZINESS); SHOULDER PAIN; SORE ARM; NAUSEA; INJECTION SITE PAIN; CALF SWELLING; This spontaneous report received from a patient concerned a 56 year old  female. The patient's height, and weight were not reported. No past medical history or concurrent conditions were reported. The patient was previously treated with influenza vaccine inact sag 3v for prophylactic vaccination.  The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 041A21A, and expiry: UNKNOWN) dose was not reported, 1 total, administered to left arm, on 05-APR-2021 for prophylactic vaccination. No concomitant medications were reported. On 05-APR-2021, at 18:00, vaccination provider gave shot on side way as she could find the muscle, immediately felt at 3 sites severe pain, at injection site, front and back of the shoulder, top of the shoulder. On the same day, after taking shot, around 14:30 minutes, patient had nausea, dizziness, and felt fainting. The vaccination provider gave her some orange juice and after 2-3 minutes later after drinking orange juice, patient felt better. Patient reported that arm remained sore for two weeks and had no other symptoms. Patient usually wore sock during night on a daily basis. On an unknown date in APR-2021, in the morning, patient noticed swelling (calf swelling) up to the sock at the line where elastic, around mid-calf area. On 28-APR-2021, at evening, patient felt heart beating out of rhythm, heart palpitation, and unusual feeling in the chest. On 29-APR-2021, she went to urgent care at 8:00. Patient was checked with electrocardiogram (EKG) machine, took blood test. Physician Assistance advised patient to go to emergency room (ER). On the report, it said vital signs noted as afebrile and cardio no rubs, no peripheral edema, heart rate was showing a normal rhythm with a rate in the 150s. They gave IV (intravenous) and bunch of fluids. On the same day, patient went to emergency room around 10:00. Patient was connected with EKG machine, had blood test and covid test, and monitored heart around 11:00, arterial fluttered atrium beating 2 times faster than ventricles high based on chest and no other issue. Patient was mildly sedated and was performed cardio version. Patient woke up around 13:30 and did not feel heart beating unusual way. Patient was discharged on same day from emergency room referred to cardio electro physiologist. Patient was given prescription medication metoprolol tartrate 25 mg take 1 tablet 2 times a day dispensing quantity 30, blood thinner xeralto 20 mg take 1 tablet by mouth once daily 30 tablets but patient did not buy medication. Physician said patient had risk of clotting. Laboratory data included: Blood test (NR: not provided) Unknown, COVID-19 virus test (NR: not provided) Unknown, Cardiac monitoring (NR: not provided) Arterial fluttered Atrium beating 2 times faster than ventricles high, EKG (NR: not provided) 150, and Vital signs measurement (NR: not provided) afebrile. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient recovered from sore arm on APR-2021, and injection site pain, and the outcome of nausea, calf swelling, artrial flutter (heart rate high, heart palpitations, felt fainting, dizziness), shoulder pain was not reported. This report was serious (Other Medically Important Condition).; Sender's Comments: V0: 20210557841-covid-19 vaccine ad26.cov2.s-artrial flutter (heart rate high, heart palpitations, felt fainting, dizziness). This event(s) is considered unassessable. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s).