transverse myelitis/urinary incontinence/inflammation in his lower back/Pain/severe difficulty walking; frontal headache/ throbbing headache; This spontaneous case was reported by a patient family member or friend and describes the occurrence of MYELITIS TRANSVERSE (transverse myelitis/urinary incontinence/inflammation in his lower back/Pain/severe difficulty walking) in a 26-year-old male patient who received mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (batch no. 205F23-2A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included COVID-19 (hospitalized in out of country hospital for 10 days) in January 2023. Previously administered products included for Product used for unknown indication: Influenza vaccine (4 weeks prior to 24Sep2023) in 2023; for COVID-19: Remdesivir. Past adverse reactions to the above products included No adverse event with Influenza vaccine and Remdesivir.    On 24-Sep-2023 at 3:00 PM, the patient received fifth dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (unknown route) 1 dosage form. On 25-Sep-2023, the patient experienced MYELITIS TRANSVERSE (transverse myelitis/urinary incontinence/inflammation in his lower back/Pain/severe difficulty walking) (seriousness criterion medically significant) and HEADACHE (frontal headache/ throbbing headache). At the time of the report, MYELITIS TRANSVERSE (transverse myelitis/urinary incontinence/inflammation in his lower back/Pain/severe difficulty walking) and HEADACHE (frontal headache/ throbbing headache) had not resolved.        For mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (Unknown), the reporter did not provide any causality assessments.   No concomitant medications were reported. The patient received other vaccines in the 4 weeks prior to COVID-19 vaccine. Monday evening is when the symptoms started. patient had severe difficulty walking and urinary incontinence. The physician stated it is related to the vaccine. It was reported patient experienced urinary incontinence while trying to walk to the bathroom. Patient using a cane to assist in walking as a daily aid, It's difficult. Patient gets pains as well when walks like an electric shock. It radiates down to the leg. Patient stated that transverse myelitis was reported previously for the older Moderna vaccinations.  No treatment medications were reported.  Company Comment: This is a Spontaneous case reported by a patient, concerning a 26-year-old male patient, with no relevant medical history, who experienced the unexpected and serious (due to medically significant) AESI of Myelitis transverse, which occurred 1 day after mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) vaccine, administered as fifth dose within COVID-19 vaccination schedule. As reported, patient experienced severe difficulty walking and urinary incontinence. He now uses a cane to assist in walking as a daily aid. He has inflammation in his lower back. He has a frontal headache and a throbbing headache intermittently in the back of his head. He gets pains as well when he walks, like an electric shock that radiates down to his leg. No information disclosed about diagnostic tests performed. At the time of the report, the event had not resolved. The benefit-risk relationship of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 29-Sep-2023: Live follow-up received that contains no new medically significant information. reference ids were added.