Irregular menses; lots of spotting recently; Dizziness; Exacerbation of her multiple sclerosis; Progressive leg weakness; Weaker than normal; This spontaneous case was reported by a physician and describes the occurrence of MULTIPLE SCLEROSIS (Exacerbation of her multiple sclerosis) 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.     The patient's past medical history included Multiple sclerosis and Reaction to previous exposure to any vaccine.    On 26-Aug-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 09-Sep-2021, the patient experienced MULTIPLE SCLEROSIS (Exacerbation of her multiple sclerosis) (seriousness criterion medically significant), MUSCULAR WEAKNESS (Progressive leg weakness), ASTHENIA (Weaker than normal) and DIZZINESS (Dizziness). On an unknown date, the patient experienced MENSTRUATION IRREGULAR (Irregular menses) and INTERMENSTRUAL BLEEDING (lots of spotting recently). The patient was treated with METHYLPREDNISOLONE SODIUM SUCCINATE (SOLUMEDROL) for Adverse event, at an unspecified dose and frequency. At the time of the report, MULTIPLE SCLEROSIS (Exacerbation of her multiple sclerosis), MUSCULAR WEAKNESS (Progressive leg weakness), ASTHENIA (Weaker than normal), MENSTRUATION IRREGULAR (Irregular menses), INTERMENSTRUAL BLEEDING (lots of spotting recently) and DIZZINESS (Dizziness) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In September 2021, Blood test: normal (normal) blood work with no abnormal findings.. In September 2021, Physical examination: abnormal (abnormal) weaker than normal.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   No concomitant medication information provided.  For the past 7 days Patient had experienced progressive leg weakness and dizziness. Leg weakness was mostly over the past 48 hours, and felt similar to past MS exacerbations.  Reported that, brain and spine MRI ordered but those have not been done yet.  Patient's husband does not think patient was pregnant.  Patient had a known prior vaccine sensitivity but was instructed by neurologist to get the vaccine anyways.  Company comment: This case concerns a patient of 51-year-old female patient with relevant medical history of who experienced the unexpected event of Exacerbation of her multiple sclerosis. The event occurred 14 days after the first dose of the administration of mRNA-1273. The rechallenge was not applicable considering that the patient was not eligible for second dose at the time of the events. Causality for the reported events was not provided by the reporter. The benefit-risk relationship of mRNA-1273 is not affected by this report.  Some vaccines have been found to be associated with reactivation of some immune mediated diseases.; Sender's Comments: This case concerns a patient of 51-year-old female patient with relevant medical history of who experienced the unexpected event of Exacerbation of her multiple sclerosis. The event occurred 14 days after the first dose of the administration of mRNA-1273. The rechallenge was not applicable considering that the patient was not eligible for second dose at the time of the events. Causality for the reported events was not provided by the reporter. The benefit-risk relationship of mRNA-1273 is not affected by this report.  Some vaccines have been found to be associated with reactivation of some immune mediated diseases.