autoimmune encephalitis; epileptic seizures; Epileptic seizure; Lost 10 pounds; Vomiting; Nausea; This spontaneous case was reported by a consumer (subsequently medically confirmed) and describes the occurrence of AUTOIMMUNE ENCEPHALOPATHY (autoimmune encephalitis), EPILEPSY (Epileptic seizure) and EPILEPSY (epileptic seizures) in a 20-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 in July 2020. Concomitant products included ORAL CONTRACEPTIVE NOS for Birth control.   On 29-Apr-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 08-May-2021, the patient experienced EPILEPSY (Epileptic seizure) (seriousness criteria hospitalization, medically significant and life threatening). On 10-May-2021, the patient experienced EPILEPSY (epileptic seizures) (seriousness criteria hospitalization, medically significant and life threatening). On an unknown date, the patient experienced AUTOIMMUNE ENCEPHALOPATHY (autoimmune encephalitis) (seriousness criteria hospitalization and medically significant), WEIGHT DECREASED (Lost 10 pounds), VOMITING (Vomiting) and NAUSEA (Nausea). The patient was hospitalized from 08-May-2021 to 09-May-2021 due to EPILEPSY, and then on 10-May-2021 due to EPILEPSY. At the time of the report, AUTOIMMUNE ENCEPHALOPATHY (autoimmune encephalitis), EPILEPSY (Epileptic seizure) and EPILEPSY (epileptic seizures) outcome was unknown and WEIGHT DECREASED (Lost 10 pounds), VOMITING (Vomiting) and NAUSEA (Nausea) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In October 2020, SARS-CoV-2 antibody test: positive (Positive) positive. On 09-May-2021, Magnetic resonance imaging: unknown (Inconclusive) unknown.         Concomitant medication included unspecified thyroid medication. The patient recovered on  06 May2021.  Afterwards, a few days later the patient was hospitalized on  08 May2021 for what was described as an epileptic seizure.  They proceeded to leave the hospital on 09 May2021 needing an MRI within the next two weeks.  The patient was re-hospitalized at 9:00AM on 10May2021 for another epileptic seziure.  They are currently examining her for an autoimmune encephalitis.  The patient proceeded to recover and was tested for antibodies in October to which it was determined they did have antibodies.  On an unknown date, and electroencephalogram was performed (results not provided).  Action taken with mRNA-1273 in response to the drug was not applicable as the patient received both planned doses.  Based on the current available information and temporal association between the use of the product and the start date of the event/s, 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/s, a causal relationship cannot be excluded.