Heart fluttering; Heart issue; Severe chest pain; Inappropriate route of vaccination; This case was initially received via another Manufacturer (Reference number: PVIUS2021001184) on 18-Aug-2021. The most recent information was received on 07-Sep-2021 and was forwarded to Moderna on 07-Sep-2021. The license partner had received the report from VAERS (Reference number: 1638756).    This regulatory authority case was reported by an other health care professional and describes the occurrence of CARDIAC FLUTTER (Heart fluttering) in a 54-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 9LU-18343-69467) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Arrhythmia, Blood pressure high and Asthma.    On 29-Apr-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous) .5 milliliter. On 29-Apr-2021, the patient experienced CARDIAC FLUTTER (Heart fluttering) (seriousness criterion medically significant), CARDIAC DISORDER (Heart issue), CHEST PAIN (Severe chest pain) and INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Inappropriate route of vaccination). The patient was treated with LORAZEPAM for Adverse event, at an unspecified dose and frequency. At the time of the report, CARDIAC FLUTTER (Heart fluttering), CARDIAC DISORDER (Heart issue) and CHEST PAIN (Severe chest pain) had not resolved and INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Inappropriate route of vaccination) had resolved.        mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous) dosing remained unchanged.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous), the reporter did not provide any causality assessments.   Concomitant medication of the patient was not reported.  No treatment information was provided by the reporter.  Company Comment: Based on the current available information and temporal association between the use of the product mRNA-1273 and the start date of the serious unexpected event of Cardiac flutter and non-serious events of Cardiac disorder and Chest pain, a causal relationship cannot be excluded; however case causality is confounded by the patient's known history of arrhythmia and hypertension. Causality for the event Incorrect route of product administration assessed as not applicable.   Most recent FOLLOW-UP information incorporated above includes: On 18-Aug-2021: Follow up received included new event added. On 07-Sep-2021: The report type of this case was updated from spontaneous to regulatory authority. Event onset date for the event Heart issue and Severe chest pain were added. Outcome for the events Heart fluttering, Heart issue and Severe chest pain were updated.; Sender's Comments: Based on the current available information and temporal association between the use of the product mRNA-1273 and the start date of the serious unexpected event of Cardiac flutter and non-serious events of Cardiac disorder and Chest pain, a causal relationship cannot be excluded; however case causality is confounded by the patient's known history of arrhythmia and hypertension. Causality for the event Incorrect route of product administration assessed as not applicable.