Had bladder infection; Felt achy; I had atrial fibrillation; Symptoms like I had the flu; General Malaise; My sense of taste went gone; Experienced some confusion as well; Trouble keeping dates straight; This spontaneous case was reported by a consumer and describes the occurrence of ATRIAL FIBRILLATION (I had atrial fibrillation) in a 92-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 042120A and 031120A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. Concomitant products included METOPROLOL, APIXABAN (ELIQUIS), AMITRIPTYLINE and LISINOPRIL for an unknown indication. On 20-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 21-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 21-Feb-2021, the patient experienced ATRIAL FIBRILLATION (I had atrial fibrillation) (seriousness criterion medically significant), INFLUENZA LIKE ILLNESS (Symptoms like I had the flu), MALAISE (General Malaise), AGEUSIA (My sense of taste went gone), CONFUSIONAL STATE (Experienced some confusion as well), DYSCALCULIA (Trouble keeping dates straight) and MYALGIA (Felt achy). On an unknown date, the patient experienced CYSTITIS (Had bladder infection). At the time of the report, ATRIAL FIBRILLATION (I had atrial fibrillation), INFLUENZA LIKE ILLNESS (Symptoms like I had the flu), MALAISE (General Malaise), AGEUSIA (My sense of taste went gone), CONFUSIONAL STATE (Experienced some confusion as well), DYSCALCULIA (Trouble keeping dates straight), CYSTITIS (Had bladder infection) and MYALGIA (Felt achy) outcome was unknown.            Action taken with mRNA-1273 in response to the events was not applicable.  Treatment information was not provided.  Company comment: Alternative explanation is that the serious unexpected event of Atrial fibrillation was more consistent with the increased risk due to underlying hypertension noted by concomitant antihypertensive therapy. The events Malaise, Ageusia, Confusional state, Dyscalculia were more consistent with Atrial fibrillation. The events Cystitis and Influenza like illness were more consistent with the environmentally mediated infection. Based on the current available information and temporal association between the use of the product and the start date of the event, Myalgia, a causal relationship cannot be excluded.   Most recent FOLLOW-UP information incorporated above includes: On 24-Jun-2021: Upon internal review on 08-DEC-2022 non-significant corrections performed to update "case received from field" to blank; Sender's Comments: Alternative explanation is that the serious unexpected event of Atrial fibrillation was more consistent with the increased risk due to underlying hypertension noted by concomitant antihypertensive therapy. The events Malaise, Ageusia, Confusional state, Dyscalculia were more consistent with Atrial fibrillation. The events Cystitis and Influenza like illness were more consistent with the environmentally mediated infection. Based on the current available information and temporal association between the use of the product and the start date of the event, Myalgia, a causal relationship cannot be excluded.