Blood pressure of systolic value of 200 mm Hg; Difficulty speaking; No reflexes anywhere; Could not lift his arms; Difficulty walking; Sciatica, "spasms in my legs, with neuropathic pain as well as muscle cramps"; Numbness and tingling on his feet and toes/numbness or paraesthesia that went up to wrists, feet and ankles; Feet and ankles followed by what noticed to be muscle weakness/ Was unable to climb stairs and noticing proximal arm weakness when lifting something over his head; Numbness and tingling on his feet and toes/numbness or paraesthesia that went up to wrists, feet and ankles; Lower back pain/back pain; Headache/headaches; Fatigue/Waking up weary; Muscle aches; This spontaneous case was received on 16-Nov-2022 from physician via Communications (reference number: SEQW22-05851) and concerned a 58-year-old, male patient.  The patient's concurrent conditions included hypertension, reflux, hypercholesterolemia and hair loss namely male pattern baldness. The patient's past medical history included nasopharyngeal carcinoma in 2002 for which the patient received chemotherapy and radiation therapy and had been in remission for 20 years. The patient's historical procedure included knee arthroscopy in 1996. The patient's concomitant medications included Propecia (finasteride) for hair loss, namely male pattern baldness and Prilosec (omeprazole) for reflux, lisinopril, simvastatin, Synthroid (levothyroxine sodium), finasteride, vitamin d3, all used for unreported indications.  On 04-Oct-2022, the patient was vaccinated with Flucelvax Quadrivalent (influenza vaccine inact sag 4v; dose: 0.5 ml, anatomical location: left deltoid muscle and route of administration: not reported) for prevention of influenza disease caused by influenza virus subtypes A and B contained in the vaccine. The batch number reported was 942394.  On 18-Oct-2022, two weeks after receiving Flucelvax Quadrivalent, the patient experienced fatigue, back pain and headache that forced him to go to bed much earlier than he was used to.   On 28-Oct-2022, the patient started developing numbness and tingling on feet and toes claiming that progressed to numbness and paraesthesia that went up to wrist, feet and ankles, followed by muscle weakness.  On an unspecified date in 2022, the patient experienced muscle aches and headaches, both treated with Tylenol (paracetamol). The patient also took ephedrine for headache.  On 02-Nov-2022, the patient got to the point where he was having difficulty walking.  On 03-Nov-2022, the patient was unable to climb stairs and started noticing proximal arm weakness when lifting something over his head.  On 04-Nov-2022, the patient reported that he was waking up weary and had difficulty showering.   On the same day, the patient was admitted to hospital and had been subjected to an antimicrobial resistance (AMR) exam. In addition, his blood pressure was measured resulting in a systolic value of 200 mmHg. When the doctor went to see the patient, he had no reflexes anywhere. Magnetic resonance imaging (MRI) was negative for nerve compression. Then the patient was subjected to lumbar puncture and had difficulty speaking. After that, the patient underwent neurological exam by three different neurologists and received intravenous immune globulin (IVIG) for five days. In conclusion, the patient stated that he could not lift his arms, but denied swallowing difficulties, and did not have respiratory problems nor did experience diarrhea.   On an unspecified date in Nov-2022, during hospitalization, the patient experienced lower back pain and sciatica with spasms in legs, with neuropathic pain as well as muscle cramps which led to treatment with baclofen in a dose of 10 mg twice daily, gabapentin in a dose of 300 mg three times per day (600mg at night for the spasms and the pain) and short-acting muscle relaxer tizanidine in a dose of 4 mg.  On an unspecified date in Nov-2022, while in hospital, the patient was tested negative for Covid-19 influenza. The patient declaimed taking the COVID vaccine.  On 09-Nov-2022, the patient was discharged from hospital and transferred to inpatient rehabilitation.  On 14-Nov-2022, the patient was discharged from inpatient rehabilitation.  At the time of initial reporting, the patient had not recovered from the events of 'muscular weakness', 'tingling' and 'numbness' and was recovering from other events. As reported, the patient still had weakness, walking had improved significantly, and arms were stronger. The patient felt much better, but still had paraesthesia and numbness on fingertips and the bottom of feet, although it went all the way to the ankle.  The reporter did not provide a causality assessment.  All events were assessed as serious due to seriousness criterion of hospitalization. The event of 'blood pressure systolic increased' was considered to be medically significant by a Physician within Seqirus's Pharmacovigilance and Risk Management Department.  Company comment: A 58-year-old, male patient was vaccinated with the suspect product Flucelvax Quadrivalent. Two weeks after vaccination the patient developed fatigue, back pain and headache. After 10 additional days the patient developed hypoaesthesia and paraesthesia initially on feet and toes, and went up to wrist, feet and ankles, followed by muscle weakness. On an unspecified day after vaccination the patient additionally developed myalgia. Twenty-nine days after vaccination the patient's condition progressed and he was having walking difficulty. The patient also reported decreased mobility due to the reported events. One month after vaccination the patient was admitted for increased systolic blood pressure (200 mm Hg as reported), and additionally developed areflexia and difficulty speaking. Magnetic resonance imaging was negative for nerve compression as reported. The patient was treated with intravenous immune globulin. During hospitalization, the patient experienced sciatica with associated muscle cramps. Underlying medical history is significant for hypertension. Due to unsuggestive temporal relationship, causality for the event sciatica is assessed as not related.  Based on presented information and plausible temporal relationship, causality for the remaining events is assessed as possibly related. Limited information precludes assessment of Brighton Collaboration criteria for Guillain-Barré Syndrome.; Sender's Comments: A 58-year-old, male patient was vaccinated with the suspect product Flucelvax Quadrivalent. Two weeks after vaccination the patient developed fatigue, back pain and headache. After 10 additional days the patient developed hypoaesthesia and paraesthesia initially on feet and toes, and went up to wrist, feet and ankles, followed by muscle weakness. On an unspecified day after vaccination the patient additionally developed myalgia. Twenty-nine days after vaccination the patient's condition progressed and he was having walking difficulty. The patient also reported decreased mobility due to the reported events. One month after vaccination the patient was admitted for increased systolic blood pressure (200 mm Hg as reported), and additionally developed areflexia and difficulty speaking. Magnetic resonance imaging was negative for nerve compression as reported. The patient was treated with intravenous immune globulin. During hospitalization, the patient experienced sciatica with associated muscle cramps. Underlying medical history is significant for hypertension. Due to unsuggestive temporal relationship, causality for the event sciatica is assessed as not related.  Based on presented information and plausible temporal relationship, causality for the remaining events is assessed as possibly related. Limited information precludes assessment of Brighton Collaboration criteria for Guillain-Barré Syndrome.