pain; dizziness,Lightheaded; Pericardial Effusion; pericarditis,minimal trace; This spontaneous case was reported by a consumer and describes the occurrence of PERICARDIAL EFFUSION (Pericardial Effusion) and PERICARDITIS (pericarditis,minimal trace) in a 51-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 006B21A and 006M20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included Mitral valve disease NOS.   On 17-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 17-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 05-Nov-2021, the patient experienced PERICARDIAL EFFUSION (Pericardial Effusion) (seriousness criterion medically significant). In November 2021, the patient experienced PERICARDITIS (pericarditis,minimal trace) (seriousness criterion medically significant). On an unknown date, the patient experienced PAIN (pain) and DIZZINESS (dizziness,Lightheaded). At the time of the report, PERICARDIAL EFFUSION (Pericardial Effusion), PAIN (pain) and DIZZINESS (dizziness,Lightheaded) had not resolved and PERICARDITIS (pericarditis,minimal trace) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 04-Nov-2021, Echocardiogram: pericardial effusion (abnormal) Pericardial Effusion.         No concomitant medications information was reported. It is reported that the patient had scheduled for the booster dose next week. On 12-Nov-2021  stress test, was done, results not provided. EKG was also done, results not provided. No treatment medications were provided.  Company Comment This case concerns a 51-year-old, female patient with no relevant medical history reported, who experienced the expected serious AESI event of Pericarditis and the unexpected serious event of Pericardial effusion. The events occurred approximately 8 months after the second dose of mRNA-1273 vaccine. The rechallenge was not applicable since the events happened after the second dose and no information on additional dosing is available. The interval between the vaccination and the occurrence events is long, however there were no other reported alternative explanations for the events. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. Case was assessed as serious due to important medical event and medical judgement.; Sender's Comments: This case concerns a 51-year-old, female patient with no relevant medical history reported, who experienced the expected serious AESI event of Pericarditis and the unexpected serious event of Pericardial effusion. The events occurred approximately 8 months after the second dose of mRNA-1273 vaccine. The rechallenge was not applicable since the events happened after the second dose and no information on additional dosing is available. The interval between the vaccination and the occurrence events is long, however there were no other reported alternative explanations for the events. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. Case was assessed as serious due to important medical event and medical judgement.