aphasia; sweating; loss of bladder control; tremors; diffuse atrophy and white matter; positive for bacteria; moderate leukocytes; small vessel ischemic change; fatigue; weakness; loss of appetite; Initial information was received on 16-Oct-2023 regarding an unsolicited valid  serious case received from a other health professional.  This case involves a 81 years old female patient who experienced aphasia, sweating, loss of bladder control, tremors, diffuse atrophy and white matter, small vessel ischemic change, positive for bacteria, moderate leukocytes, fatigue, weakness and loss of appetite after receiving influenza quadrival A-B high dose HV vaccine [Fluzone high-dose quadrivalent].  The patient's past medical history, medical treatment(s), vaccination(s) and family history were not provided.  On 09-Oct-2023, the patient received a 0.7 ml dose of suspect influenza quadrival A-B high dose HV vaccine (unknown formulation) (lot UT8131DA, expiration date: 30-Jun-2024, unknown strength) via intramuscular route in the left deltoid for Immunization.  On 09-Oct-2023 the patient had aphasia, sweating (hyperhidrosis), loss of bladder control (urinary incontinence), tremors (tremor), diffuse atrophy and white matter (atrophy), small vessel ischemic change (vasculitis), positive for bacteria (bacterial test positive), moderate leukocytes (white blood cell disorder), fatigue, weakness (asthenia), loss of appetite (decreased appetite) (Latency: same day) following the administration of influenza quadrival A-B high dose HV vaccine.  Relevant laboratory test results included: Blood work:  On an unknown date:  [Unknown] Angiogram - On an unknown date:  [no large vessel occlusions, no critical stenosis, no vascular malfunctions or aneurysms] Chest X-ray - On an unknown date:  [Unknown] Computerised tomogram - On an unknown date:  [Diffuse atrophy and white matter, small vessel ischemic change, no evidence of acute intracranial disease] Echocardiogram - On an unknown date:  [Unknown] Lumbar puncture - On an unknown date:  [Unknown] Magnetic resonance imaging - On an unknown date:  [Unknown] Urine analysis - On an unknown date:  [Positive for bacteria, moderate leukocytes, negative nitrites, culture pending]  Action taken: not applicable.  The patient was treated with acetylsalicylic acid (aspirin), ceftriaxone sodium (rocephin iv), ciprofloxacin and doxycycline, Neuro checks, seizure precautions, speech therapy, occupational therapy, physical therapy.  At time of reporting, the outcome was Not Recovered / Not Resolved for the events.  Seriousness Criteria: Hospitalization for all events except loss of appetite. (Hospitalization was from 09-Oct -2023 to 14-Oct-2023, duration: 5 days).; Sender's Comments: Sanofi Company Comment dated 22-Oct-2023: This case involves a 81 years old female patient who experienced aphasia, sweating, loss of bladder control, tremors, diffuse atrophy and white matter, small vessel ischemic change, positive for bacteria, moderate leukocytes, fatigue, weakness and loss of appetite after receiving influenza quadrival A-B high dose HV vaccine [Fluzone high-dose quadrivalent]. Further information on medical history, allergy history, family history, past or concomitant medication excluding alternative etiologies for the reported event are needed to fully assess this case. Based upon the limited reported information, the role of the individual suspect vaccine cannot be assessed.