Guillain-Barre syndrome; This is a literature case initially received on 06-Jan-2020, concerning 67-year-old, male patient.   The literature citation:One in a million: Guillain-Barre syndrome.  The patient's medical history included hypertension, hyperlipidaemia, emphysema, and gastroesophageal reflux disease. Patient did not have recent respiratory or gastrointestinal infections, surgery, trauma, HIV, or constitutional symptoms.  The patient's concomitant medications were not reported.  On an unknown date, the patient was administered INN Flu Vaccine Seasonal [influenza virus vaccine polyvalent; dose, route of administration and anatomical location, batch number, and expiry date: not reported] for an unknown indication.   On an unknown date the patient presented with complaints of abdominal distention and tingling sensation of both hands and feet.   On the next days, two weeks after vaccination, the patient was admitted to a hospital.   After admission the initial physical examination was unremarkable for diminished motor strength in upper (3/5) and lower extremities (2/5) accompanied by areflexia.   On an unknown date, during hospitalization the patient's condition worsened with subsequent development of ataxia as well as generalized weakness.  Thirty-six hours after admission, the patient developed respiratory muscle weakness with worsening negative inspiratory force (NIF) and subsequent hypercapnic respiratory failure requiring endotracheal intubation.  On an unknown date, the patient underwent laboratory evaluation which was unremarkable and head computerised tomography (CT) scan which did not suggest acute intracranial event.   The patient also underwent cerebrospinal fluid (CSF) analysis which failed to reveal albuminocytologic dissociation or any acute infectious process and electromyography to evaluate for polyneuropathy revealed delayed distal latencies, decreased velocity, and absent F waves suggestive of an acute demyelinating polyneuropathy.  This case was recognized as Guillain-Barre syndrome, potential complication of influenza vaccine.   On an unknown date, the patient was treated with intravenous immunoglobulins (IVIGs) for 5 days, but he did not wean from mechanical ventilation, so tracheostomy was performed, along with a percutaneous endoscopic gastrostomy due to dysphagia.   The patient also had two additional courses of IVIGs and one course of plasmapheresis were administered which led to weaning of mechanical ventilation and improvement of motor function.   On an unknown date the patient was discharged on physical rehabilitation and was recovering from the event.   Per company, the event of Guillain-Barre syndrome was assessed as serious due to the criterion of medical significance and hospitalisation.  The reporter considered the event of Guillain-Barre syndrome as related to INN Flu Vaccine Seasonal.  Company comment: The patient experienced Guillain-Barre syndrome after vaccination with the suspect product, INN Flu Vaccine Seasonal. Chronology is plausible. No concomitant medications were provided. Considering all the above mentioned, causality between suspect product and the event is assessed as related.; Sender's Comments: The patient experienced Guillain-Barre syndrome after vaccination with the suspect product, INN Flu Vaccine Seasonal. Chronology is plausible. No concomitant medications were provided. Considering all the above mentioned, causality between suspect product and the event is assessed as related.