Doctors mentioned she had atrial fibrillation; Interchange of vaccine products; Revaccination with different COVID-19 vaccine; This spontaneous case was reported by a consumer and describes the occurrence of ATRIAL FIBRILLATION (Doctors mentioned she had atrial fibrillation) in an 81-year-old female patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (batch no. 024H22A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.    Co-suspect product included non-company product METOPROLOL TARTRATE (METOPROLOL ABZ) for Blood pressure increased.    Previously administered products included for Drug use for unknown indication: PFIZER BIONTECH COVID-19 VACCINE (Dose 1), PFIZER BIONTECH COVID-19 VACCINE (Dose 4), Pfizer (Dose 3) and Pfizer (Dose 2). Past adverse reactions to the above products included No adverse event with PFIZER BIONTECH COVID-19 VACCINE, PFIZER BIONTECH COVID-19 VACCINE, Pfizer and Pfizer. Concurrent medical conditions included Scoliosis (Scoliosis (patient was on painkillers to treat this condition,) and Blood pressure high (high blood pressure, patient takes Metoprolol.). Concomitant products included IBUPROFEN, PSEUDOEPHEDRINE HYDROCHLORIDE (ADVIL CS) and PARACETAMOL (TYLENOL) for Scoliosis.   On 22-Nov-2022, the patient received fifth dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) 1 dosage form. On an unknown date, the patient started METOPROLOL TARTRATE (METOPROLOL ABZ) (unknown route) at an unspecified dose. On 26-Nov-2022, the patient experienced ATRIAL FIBRILLATION (Doctors mentioned she had atrial fibrillation) (seriousness criteria hospitalization and medically significant). On an unknown date, the patient experienced INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine). The patient was hospitalized from sometime in November 2022 to 30-Nov-2022 due to ATRIAL FIBRILLATION. The patient was treated with ACETYLSALICYLIC ACID (ASPIRIN N) ongoing since an unknown date for Atrial fibrillation, at an unspecified dose and frequency and APIXABAN (ELIQUIS) for Atrial fibrillation, at an unspecified dose and frequency. At the time of the report, ATRIAL FIBRILLATION (Doctors mentioned she had atrial fibrillation) had not resolved and INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine) outcome was unknown.        For mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (Unknown), the reporter did not provide any causality assessments.   On unknown date, patient had lab test EKG for which result was unknown. Patient had not receive any other vaccines in the 4 weeks prior to COVID-19 vaccine. The symptoms of atrial fibrillation included chest pain. On 26-Nov-2022, the patient stated that she experienced fluttering of the heart and pain in the chest area, and she went to ER where doctors made an EKG and gave her aspirin. Symptoms stopped on 28-Nov-2022. Doctors mentioned she had atrial fibrillation. She was released from the hospital on 30-Nov-2022. The patient's husband asked how long it would take for his wife's symptoms to go away.  No treatment medication was provided  Company comment: This spontaneous case concerns an 81-year-old female patient with relevant medical history of hypertension, who experienced serious (medically significant and hospitalization) unexpected event of atrial fibrillation, that occurred approximately 4 days after a dose of the mRNA-1273 Bivalent, 5th dose in vaccination series. Additionally, there was an interchange of vaccine products due to revaccination with different COVID-19 vaccine since the patient had been previously vaccinated with 4 doses of Pfizer BioNTech COVID-19 vaccine. Reportedly, the patient developed heart fluttering and chest pain and went to ER where ECG was performed and aspirin administered. ECG results were not provided. The patient was subsequently hospitalized and discharged after 4 days. The doctors mentioned that the patient had atrial fibrillation and was also prescribed with Eliquis (apixaban). Initially, it was reported that the symptoms resolved 2 days prior to discharge however, the patient called at a later date to ask how long it takes for side effects to go away, implying that the symptoms did not resolve. The patient's advanced age and relevant medical history is a possible confounder. The benefit-risk relationship of mRNA-1273 is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 13-Dec-2022: Live Significant follow up received include suspect Lot number updated; Sender's Comments: This spontaneous case concerns an 81-year-old female patient with relevant medical history of hypertension, who experienced serious (medically significant and hospitalization) unexpected event of atrial fibrillation, that occurred approximately 4 days after a dose of the mRNA-1273 Bivalent, 5th dose in vaccination series. Additionally, there was an interchange of vaccine products due to revaccination with different COVID-19 vaccine since the patient had been previously vaccinated with 4 doses of Pfizer BioNTech COVID-19 vaccine. Reportedly, the patient developed heart fluttering and chest pain and went to ER where ECG was performed and aspirin administered. ECG results were not provided. The patient was subsequently hospitalized and discharged after 4 days. The doctors mentioned that the patient had atrial fibrillation and was also prescribed with Eliquis (apixaban). Initially, it was reported that the symptoms resolved 2 days prior to discharge however, the patient called at a later date to ask how long it takes for side effects to go away, implying that the symptoms did not resolve. The patient's advanced age and relevant medical history is a possible confounder. The benefit-risk relationship of mRNA-1273 is not affected by this report.