Post-Vaccination Acute Disseminated Encephalomyelitis; acute onset of confusion; expressive aphasia and was unable to follow commands; tachycardic; Initial information received on 03-Jul-2023 by health care professional from country regarding an unsolicited valid serious case issued from a literature article.  This case involves a 59 years old male patient who experienced post-vaccination acute disseminated encephalomyelitis (ADEM) (acute disseminated encephalomyelitis) while receiving vaccines COVID-19 (coronavirus 2019) VACCINE, INFLUENZA VACCINE and shingles (latency: 10 days).  The patient had history of prediabetes and dyslipidemia.  On an unknown date, patient had received vaccinations for COVID- 19, influenza, and shingles all in the same encounter produced by unknown manufacturers lot number not reported via unknown route in unknown administration site as prophylactic vaccination.   On an unknown date, the patient presented to the emergency department for acute onset of confusion (confusional state), aphasia, and inability to follow commands (aphasia) which started 10 days prior to presentation. He exhibited no focal deficits on examination however had expressive aphasia and was unable to follow commands, requiring intubation for airway protection. He was febrile to 38.4 Celcius and tachycardic to 120 bpm. Initial lab work including CBC (complete blood count), CMP (comprehensive metabolic panel), ethanol level, and urine drug screen were unremarkable except for elevated blood glucose of 294 mg/dL. MRI (Magnetic resonance imaging) brain with and without contrast demonstrated a hyperintense T2/FLAIR (Fluid-attenuated inversion recovery) signal in the bilateral temporal lobes with periventricular and deep white matter involvement. Electroencephalogram (EEG) showed diffuse slowing however was negative for epileptiform activity. Cerebrospinal fluid (CSF) revealed an elevated CSF protein at 105 mg/dL but was otherwise negative for acute process on meningitis, encephalitis, and paraneoplastic panels. Given the patient's clinical history of recent vaccination, imaging findings, and CSF studies, he was given high-dose corticosteroid therapy for post-vaccination ADEM with methylprednisolone 1000 mg intravenous (IV) daily for five days. Patient's mentation began to improve following the first dose of high dose steroids. Repeat MRI brain with and without contrast after completion of steroid course revealed complete interval resolution of the T2/FLAIR hyperintensity previously noted, and the patient had returned to his clinical baseline at the time of discharge.  Action taken: Not applicable Corrective treatment: methylprednisolone Outcome: Recovered Seriousness criteria: Medically significant and hospitalization Reporter causality: Related; Sender's Comments: Sanofi company comment dated 06-JUL-2023: This case involves a 59 years old male patient who experienced post-vaccination acute disseminated encephalomyelitis (ADEM) (acute disseminated encephalomyelitis) while receiving vaccines COVID-19 (coronavirus 2019) VACCINE, INFLUENZA VACCINE. Based on information received the causal role of VACCINES cannot be excluded due to compatible temporal relationship of ADR to the VACCINES. Furthermore, information regarding previous vaccination, tolerance, allergic history excluding alternative etiologies for the reported event are needed to fully assess this case. Based upon the reported information, the role of vaccines cannot be assessed.