Product dose omission issue; Pericarditis; Pericardial effusion; Tachycardia; feeling miserable; shortness of breath; This spontaneous case was reported by a nurse and describes the occurrence of PERICARDITIS (Pericarditis) and PERICARDIAL EFFUSION (Pericardial effusion) in a 27-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.     The patient's past medical history included COVID-19 (COVID-19 infection) and COVID-19 virus test positive (Prior to vaccine).    In December 2020, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. In December 2020, the patient experienced PERICARDITIS (Pericarditis) (seriousness criterion medically significant), PERICARDIAL EFFUSION (Pericardial effusion) (seriousness criterion medically significant), TACHYCARDIA (Tachycardia), FEELING ABNORMAL (feeling miserable) and DYSPNOEA (shortness of breath). On an unknown date, the patient experienced PRODUCT DOSE OMISSION ISSUE (Product dose omission issue). In March 2021, PERICARDITIS (Pericarditis), PERICARDIAL EFFUSION (Pericardial effusion), FEELING ABNORMAL (feeling miserable) and DYSPNOEA (shortness of breath) had resolved. At the time of the report, TACHYCARDIA (Tachycardia) had not resolved and PRODUCT DOSE OMISSION ISSUE (Product dose omission issue) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Heart rate: 130-145 (High) heart rate was 130 to 145 at rest heart rate increased.     mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was withdrawn on an unknown date.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant was provided.  The patient developed the adverse reaction the very next day of her 1st dose, and so she has not gotten her 2nd dose yet.  On the next day of her 1st dose, she was feeling miserable and heart rate was 130 to 145 at rest and developed shortness of breath and pain which felt like having a heart attack.  The patient still having episodes of tachycardia.  The patient was on some medications, but not anymore.  Reportedly, the patient did not experienced symptoms like this before receiving the Moderna COVID-19 vaccine.  This case concerns a 27 year old female with a history of COVID-19 infection in Dec 2019 who experienced the serious listed AESI of Pericarditis and serious unlisted event of Pericardial effusion and the non-serious unlisted event of Product dose omission issue. The events reportedly occurred the day after the first dose of mRNA-1273 in Dec 2020. Re-challenge is not applicable as this is dose 1. The patient as not had dose 2 yet. Benefit -risk relationship is not affected by this report.; Sender's Comments: This case concerns a 27 year old female with a history of COVID-19 infection in Dec 2019 who experienced the serious listed RA of Pericarditis and serious unlisted event of Pericardial effusion and the non-serious unlisted event of Product dose omission issue. The events reportedly occurred the day after the first dose of mRNA-1273 in Dec 2020. Re-challenge is not applicable as this is dose 1. The patient as not had dose 2 yet. Benefit -risk relationship is not affected by this report.