Atrial fibrillation; I did not feel very well; soreness in the arm, have more intense sense of pain; Flu like symptoms; I did not feel normal; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 69-year-old male patient received bnt162b2 omi xbb.1.5 (COMIRNATY (2023-2024 FORMULA)), on 09Nov2023 at 10:00 as dose 1, single (Batch/Lot number: unknown) at the age of 69 years intramuscular, in left arm for covid-19 immunisation. The patient's relevant medical history included: "Hypertension" (unspecified if ongoing); "Atrial fibrillation Paroxysmal" (ongoing). Concomitant medication(s) included: ATENOLOL oral taken for hypertension; LISINOPRIL oral taken for hypertension. Vaccination history included: Bnt162b2 (DOSE 1, SINGLE, Batch/ Lot Number: EK4176), for COVID-19 immunisation, reaction(s): "Soreness in the arm"; Bnt162b2 (DOSE 2, SINGLE, Batch/ Lot Number: EL9261), for COVID-19 immunisation, reaction(s): "Soreness in the arm"; Bnt162b2 (DOSE 3 (BOOSTER), SINGLE, Batch/ Lot Number: 30155BA), for COVID-19 immunisation, reaction(s): "Soreness in the arm"; Bnt162b2 (DOSE 4 (BOOSTER), SINGLE, Batch/ Lot Number: FJ4895), for COVID-19 immunisation, reaction(s): "Soreness in the arm"; Bnt162b2;bnt162b2 omi ba.4-5 (DOSE 5 (BOOSTER), SINGLE, Batch/ Lot Number: GJ6738), for COVID-19 immunisation, reaction(s): "Soreness in the arm". The following information was reported: MALAISE (non-serious) with onset 10Nov2023, outcome "unknown", described as "I did not feel very well"; ATRIAL FIBRILLATION (medically significant) with onset 11Nov2023 at 06:30, outcome "recovering"; INFLUENZA LIKE ILLNESS (non-serious) with onset Nov2023, outcome "unknown", described as "Flu like symptoms"; FEELING ABNORMAL (non-serious) with onset Nov2023, outcome "unknown", described as "I did not feel normal"; VACCINATION SITE PAIN (non-serious) with onset Nov2023, outcome "unknown", described as "soreness in the arm, have more intense sense of pain". The patient underwent the following laboratory tests and procedures: Electrocardiogram: (11Nov2023) Atrial fibrillation. Therapeutic measures were taken as a result of atrial fibrillation, malaise, vaccination site pain, influenza like illness, feeling abnormal. Clinical Course: Patient had a history of Atrial fibrillation paroxysmal and that morning two days after the vaccination he woke experiencing Atrial fibrillation. It was paroxysmal more, comes and goes and he not had in the very long time so it was very surprise that morning when he woke and he could not, he could felt like and he had device at home that he could measure the EKG, it was portable EKG and he measured it and that he was in Afib that morning. Patinet had took actually all her vaccination had been the Pfizer for COVID, so that was now his 6th vaccination. There was a number afterwards it was said, the first letter he was not sure if its was an M or an H but its 4589. He was looking, he was not sure its either HG or MG and that's 4589. He stated that he had history of hypertension and he was on antihypertension medications. Stated that the date of the vaccination was 09Nov, two days ago and experienced that morning (11Nov2023) he woke up and he could feel the arrythmia, almost 48 hours. He had not checked recently, checked it about half an hour ago and it was still in Afib and It was improving. Patient stated he took Aspirin. Patient did not received any vaccine on the same day of vaccination and did not recoved any vaccination with in 4 weeks. Time of vaccination: Patient stated, 10 AM and time of adverse event stated Today he realized it at 6:30 AM. With the previous vaccinations, just soreness in the arm and stated this time he had more intense sense of pain and he kind of felt, yesterday he did not feel very well and then the first day after the vaccination kind of some flu like symptoms, he would say Afib but still he felt he did not feel normal, yesterday. No, that was it he just wanted to report for all the vaccination that he received related to COVID for Pfizer that one was the most intense reaction, post vaccination he had. He took an analgesic. he had Excedrin which was Tylenol with aspirin. He took that yesterday. That morning when he started the Afib, he actually he took two aspirin, kind of prophylactically.The expiration was 18Jun and so he guess that was two years ago did not realized that.   The information on the batch/lot number for [BNT162B2 OMI XBB.1.5] has been requested and will be submitted if and when received.; Sender's Comments: Linked Report(s) : US-PFIZER INC-202300367425 same patient, different vaccine dose number/different event;US-PFIZER INC-202300367427 same patient, different vaccine dose number/different event;US-PFIZER INC-202300367426 same patient, different vaccine dose number/different event;US-PFIZER INC-202300367428 same patient, different vaccine dose number/different event;US-PFIZER INC-202300367424 same patient, different vaccine dose number/different event;