palpitation; has just been tired since then/lingering tiredness; tachycardia; did not take the second dose; This spontaneous case was reported by a consumer and describes the occurrence of TACHYCARDIA (tachycardia), PALPITATIONS (palpitation) and FATIGUE (has just been tired since then/lingering tiredness) in an 82-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 011J20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Tachycardia.    On 15-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 19-Jan-2021, the patient experienced TACHYCARDIA (tachycardia) (seriousness criteria hospitalization prolonged and medically significant) and PRODUCT DOSE OMISSION ISSUE (did not take the second dose). On an unknown date, the patient experienced PALPITATIONS (palpitation) (seriousness criteria hospitalization prolonged and medically significant) and FATIGUE (has just been tired since then/lingering tiredness) (seriousness criterion hospitalization prolonged). The patient was hospitalized on sometime in February 2021 due to FATIGUE, PALPITATIONS and TACHYCARDIA. The patient was treated with METOPROLOL for Heart disorder, at an unspecified dose and frequency. At the time of the report, TACHYCARDIA (tachycardia), PALPITATIONS (palpitation), FATIGUE (has just been tired since then/lingering tiredness) and PRODUCT DOSE OMISSION ISSUE (did not take the second dose) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 19-Jan-2021, Echocardiogram: did not have a heart attack. On 19-Jan-2021, Enzyme level test: high (High) High. On 19-Jan-2021, Heart rate: high (High) 140 and 150.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.       No concomitant medications were provided. The patient was  hospitalized for day and a half where  they catharized her and did an echocardiogram.  This is a case of product dose omission for this 82-year-old, female patient with medical history of tachycardia who experienced the unexpected event of tachycardia, palpitation and the expected event of fatigue.  The events started 4 days after the first dose of Spikevax. The rechallenge was not applicable, as the events happened after the first dose. The events were considered related to the product per the reporter's assessment. The medical history of tachycardia and advanced age remains as confounder. The event fatigue is consistent with the current understanding of the mechanism of action of the vaccine. The benefit-risk relationship of Spikevax in not affected by this report.; Sender's Comments: This is a case of product dose omission for this 82-year-old, female patient with medical history of tachycardia who experienced the unexpected event of tachycardia, palpitation and the expected event of fatigue.  The events started 4 days after the first dose of Spikevax. The rechallenge was not applicable, as the events happened after the first dose. The events were considered related to the product per the reporter's assessment. The medical history of tachycardia and advanced age remains as confounder. The event fatigue is consistent with the current understanding of the mechanism of action of the vaccine. The benefit-risk relationship of Spikevax in not affected by this report.