transverse myelitis which may be due to the vaccine; weakness of the right arm and leg; This spontaneous case was reported by a physician and describes the occurrence of MYELITIS TRANSVERSE (transverse myelitis which may be due to the vaccine) in a 63-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 013L20A and 039K20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 14-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 13-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In January 2021, the patient experienced MUSCULAR WEAKNESS (weakness of the right arm and leg). On an unknown date, the patient experienced MYELITIS TRANSVERSE (transverse myelitis which may be due to the vaccine) (seriousness criterion medically significant). At the time of the report, MYELITIS TRANSVERSE (transverse myelitis which may be due to the vaccine) and MUSCULAR WEAKNESS (weakness of the right arm and leg) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Computerised tomogram: longitudinal extensive lesion (abnormal) longitudinal extensive lesion on the right C6 and a little bit of T1 level.. On an unknown date, Lumbar puncture: negative for ig index for ms (Negative) negative for Ig index for MS. On an unknown date, Magnetic resonance imaging: did not show multiple sclerosis (Negative) did not show multiple sclerosis.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant product use was not provided by the reporter. A neurologist reported that he had a patient who complained of weakness of the right arm and leg two weeks after getting the first dose of the Moderna Covid-19 vaccine in Jan 2021. The patient had been to many doctors and he saw him in October. The cervical CT scan showed longitudinal extensive lesion on the right C6 and a little bit of T1 level. The MRI did not show multiple sclerosis. He did a spinal tap which turned out to be negative for Ig index for MS. He was thinking that this was behaving like and NMO spectrum disease. He was concerned that there was an ongoing chronic inflammation. His diagnosis was transverse myelitis which may be due to the vaccine. The patient was improving with IV steroids (was given oral steroids but no improvement was seen) and physical therapy.   This case concerns a 63-year-old male patient with relevant medical history, who experienced the unexpected serious event of Myelitis Transverse. The event, which was medically significant, occurred 2 days after receiving the first dose of mRNA-1273 Vaccine. The rechallenge was not applicable since only information about the first dose was disclosed. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.; Sender's Comments: This case concerns a 63-year-old male patient with relevant medical history, who experienced the unexpected serious event of Myelitis Transverse. The event, which was medically significant, occurred 2 days after receiving the first dose of mRNA-1273 Vaccine. The rechallenge was not applicable since only information about the first dose was disclosed. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.