Diagnosed with Atrial Fibrillation; Diagnosed with Pericarditis; This spontaneous case was reported by a consumer (subsequently medically confirmed) and describes the occurrence of ATRIAL FIBRILLATION (Diagnosed with Atrial Fibrillation) and PERICARDITIS (Diagnosed with Pericarditis) in a 79-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 029L20A and 001B21A) for COVID-19 vaccination.     No medical history was provided by the reporter.  The patient's past medical history included Stent placement (he had a stent placed 6-8 years ago.).   On 07-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 11-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 22-Mar-2021, the patient experienced ATRIAL FIBRILLATION (Diagnosed with Atrial Fibrillation) (seriousness criteria hospitalization, medically significant and life threatening) and PERICARDITIS (Diagnosed with Pericarditis) (seriousness criteria hospitalization, medically significant and life threatening). The patient was hospitalized on 22-Mar-2021 due to ATRIAL FIBRILLATION and PERICARDITIS. The patient was treated with APIXABAN (ELIQUIS) ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency; COLCHICINE ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency; BISOPROLOL ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency; ALBUTEROL [SALBUTAMOL] ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency; DISODIUM FUMARATE (FUMARATE DISODIUM) ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency; GLIPIZIDE ongoing from 22-Mar-2021 for Blood sugar increased, at an unspecified dose and frequency; FLUTICASONE FUROATE, UMECLIDINIUM BROMIDE, VILANTEROL TRIFENATATE (TRELEGY) ongoing from 22-Mar-2021 for Adverse event, at an unspecified dose and frequency and GABAPENTIN ongoing from 22-Mar-2021 for Cough, at an unspecified dose and frequency. On 25-Mar-2021, ATRIAL FIBRILLATION (Diagnosed with Atrial Fibrillation) and PERICARDITIS (Diagnosed with Pericarditis) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 22-Mar-2021, Blood glucose: high (High) High.         It was reported that Patient reports that he was diagnosed with Pericarditis and AFib 8 days after receiving the second shot on 11March2021 in his deltoid. Patient stated that on 19March2021 went to the ER with chest pain. They tested him and discharged him. On 21March2021, patient had chills, felt weak, had low energy, and on 22March2021 he had chest pain that patient didn't like so was then hospitalized. Patient had shortness of breath. It was reported that patient had a stent placed 6-8 years ago. patient had ECG, cardiac test, cardiac enzymes, Troponin level but result unknown.  patient did not have a medical history of Myocarditis/pericarditis. Diagnosed with Pericarditis and Atrial Fibrillation. Had chest pain, Shortness of breath upon exertion (walking, going up the stairs he needs to stop and catch his breath), terrible cough. Patient had chest pain, low energy, chills, felt weak, terrible cough, shortness of breath upon exertion, high blood sugar, terrible cough. He almost passed out several times from the bad coughs.  This case concerns a 79-year-old, male patient with previous relevant medical history of stent placement, who experienced the unexpected events of atrial fibrillation and pericarditis. The events occurred 11 days after the second dose of mRNA-1273 Moderna vaccine. The rechallenge was not applicable since the events happened after the second dose. The medical history of stent placement remains a confounder. The benefit-risk relationship of mRNA-1273 Moderna vaccine is not affected by this report.; Sender's Comments: This case concerns a 79-year-old, male patient with previous relevant medical history of stent placement, who experienced the unexpected events of atrial fibrillation and pericarditis. The events occurred 11 days after the second dose of mRNA-1273 Moderna vaccine. The rechallenge was not applicable since the events happened after the second dose. The medical history of stent placement remains a confounder. The benefit-risk relationship of mRNA-1273 Moderna vaccine is not affected by this report.