myocarditis; Heart palpitations a few days later after the shot for a week; The diagnosis was tachycardia; Shortness of breath/pain with breathing; Chest pain/pressure/discomfort; Chest pain/pressure/discomfort; Shortness of breath/pain with breathing; This spontaneous case was reported by a consumer and describes the occurrence of MYOCARDITIS (myocarditis) in a 51-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Previously administered products included for COVID-19 vaccination: PFIZER BIONTECH COVID-19 VACCINE (Pfizer 1st Dose: Lot number: EU6203) and PFIZER BIONTECH COVID-19 VACCINE (Pfizer 2nd Dose: Lot number: ER8730); for Product used for unknown indication: Shingle shot; for Flu vaccination: Flu shot. Past adverse reactions to the above products included No adverse event with Flu shot, PFIZER BIONTECH COVID-19 VACCINE, PFIZER BIONTECH COVID-19 VACCINE and Shingle shot. Concurrent medical conditions included Drug allergy (Codeine).    On 08-Jan-2022, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On an unknown date, the patient experienced MYOCARDITIS (myocarditis) (seriousness criterion medically significant), PALPITATIONS (Heart palpitations a few days later after the shot for a week), TACHYCARDIA (The diagnosis was tachycardia), PAINFUL RESPIRATION (Shortness of breath/pain with breathing), CHEST DISCOMFORT (Chest pain/pressure/discomfort), CHEST PAIN (Chest pain/pressure/discomfort) and DYSPNOEA (Shortness of breath/pain with breathing). At the time of the report, MYOCARDITIS (myocarditis), PALPITATIONS (Heart palpitations a few days later after the shot for a week), TACHYCARDIA (The diagnosis was tachycardia), PAINFUL RESPIRATION (Shortness of breath/pain with breathing), CHEST DISCOMFORT (Chest pain/pressure/discomfort), CHEST PAIN (Chest pain/pressure/discomfort) and DYSPNOEA (Shortness of breath/pain with breathing) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Electrocardiogram: result not provided (Inconclusive) Result not provided. On an unknown date, Myocardial necrosis marker: result not provided (Inconclusive) Result not provided. On an unknown date, Ultrasound scan: result not provided (Inconclusive) Result not provided.         Concomitant products were not provided. Treatment medication were not reported.  The lab data results were still pending until Feb 19. Patient thinks they gave her a full dose not a booster dose. Patient is still seeing doctors.  Company comment: This spontaneous case concerns a 51-year-old female patient with history of interchange of vaccine products (Pfizer biontech Covid 19 vaccine), Flu vaccination, experienced the Unexpected serious AESI event Pericarditis on an unknown date after one dose of mRNA-1273(taken as booster dose). The patient developed tachycardia, palpitations, chest pain and dyspnoea. Details of investigations/treatment were not reported. At the time of reporting, the events had not resolved. Interchange of vaccine products, and Flu vaccination remain confounders. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This spontaneous case concerns a 51-year-old female patient with history of interchange of vaccine products (Pfizer biontech Covid 19 vaccine), Flu vaccination, experienced the Unexpected serious AESI event Pericarditis on an unknown date after one dose of mRNA-1273(taken as booster dose). The patient developed tachycardia, palpitations, chest pain and dyspnoea. Details of investigations/treatment were not reported. At the time of reporting, the events had not resolved. Interchange of vaccine products, and Flu vaccination remain confounders. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.