Body went on involuntary convulsion; Felt like her brain was swollen; Feeling dizzy; Disoriented; Arm hurting very bad; Pouring out cold sweat; Extremely cold; Teeth chattering/Shivering; Body was shaking; Symptoms were worse; Fever with temperature of 104; Severe head pain; Severe muscle aches; This spontaneous case was reported by a patient and describes the occurrence of SEIZURE (Body went on involuntary convulsion) and BRAIN OEDEMA (Felt like her brain was swollen) in a 33-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 046B21A and 007B21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 13-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 11-May-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 11-May-2021, the patient experienced SEIZURE (Body went on involuntary convulsion) (seriousness criterion medically significant), BRAIN OEDEMA (Felt like her brain was swollen) (seriousness criterion medically significant), DIZZINESS (Feeling dizzy), DISORIENTATION (Disoriented), PAIN IN EXTREMITY (Arm hurting very bad), COLD SWEAT (Pouring out cold sweat), FEELING COLD (Extremely cold), CHILLS (Teeth chattering/Shivering), TREMOR (Body was shaking), CONDITION AGGRAVATED (Symptoms were worse), PYREXIA (Fever with temperature of 104), HEADACHE (Severe head pain) and MYALGIA (Severe muscle aches). At the time of the report, SEIZURE (Body went on involuntary convulsion), BRAIN OEDEMA (Felt like her brain was swollen), DIZZINESS (Feeling dizzy), DISORIENTATION (Disoriented), PAIN IN EXTREMITY (Arm hurting very bad), COLD SWEAT (Pouring out cold sweat), FEELING COLD (Extremely cold), CHILLS (Teeth chattering/Shivering), TREMOR (Body was shaking), CONDITION AGGRAVATED (Symptoms were worse), PYREXIA (Fever with temperature of 104), HEADACHE (Severe head pain) and MYALGIA (Severe muscle aches) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Body temperature: 104 (High) fever.         Reporter called on 12-May-2021 to report feeling dizzy, disoriented, her arm hurting very bad, severe muscle ache, shivering, pouring out cold sweat, she was extremely cold, had fever with temperature of 104, her body went on involuntary convulsion, her teeth chattering, her body was shaking, she had severe head pain and she felt like her brain was swollen. The symptoms started 11-May-2021 after she received her second Moderna COVID-19 vaccine on 11-May-2021 around 9am in the morning. Symptoms were worse around 10 pm evening. She took Tylenol but it did not help. She said the symptoms were still ongoing, but it was fading. She received the second vaccine in her left upper arm with vaccine lot 046B21A. She received the first vaccine on 13April 2021 in her left upper arm with vaccine lot 007B21A. She did not have a doctor.   Treatment medication included: Tylenol.  Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded.; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded.