weakness/progressive generalized muscle weakness/neuromuscular weakness of unknown etiology; respiratory failure/acute hypoxic respiratory failure; recurrent aspiration; recurrent mucus plugging; pneumonia; gastrointestinal bleeding; hemorrhagic shock; hypertension; Atrial fibrillation; possibly GBS; Eaton-Lambert syndrome; myasthenia gravis; Initial information received on 13-Mar-2021 regarding an unsolicited valid serious case from a other health professional.   This case is linked to cases 2021SA091271, 2021SA091226, 2021SA091286, 2021SA091303, 2021SA091334, 2021SA091349, 2021SA091366, 2021SA091398, 2021SA091448, 2021SA091468, 2021SA091489, 2021SA091516, 2021SA091556, 2021SA091604, 2021SA091690, 2021SA091745, 2021SA091782, 2021SA091798, 2021SA091833, 2021SA091855 and 2021SA091879. (Same Literature article)  Abstract: On October 7, 2016, the Food and Drug Administration approved recombinant hemagglutinin quadrivalent influenza vaccine (RIV4) (Spodoptera frugiperda cell line; Flublok Quadrivalent) for active immunization for the prevention of influenza disease in individuals 18 years of age and older. Clinical trials did not reveal any major differences in adverse events or serious adverse events following Flublok Quadrivalent versus standard dose quadrivalent inactivated influenza vaccine. To improve our understanding of the safety profile of this vaccine, we reviewed and summarized adverse event reports after Flublok Quadrivalent administration to the vaccine adverse event reporting system (VAERS). Through June 30, 2020, VAERS received 849 reports after RIV4 vaccination. The vast majority (810; 95%) were nonserious. Among serious events, there were 10 cases of Guillain-Barre syndrome, including 5 people who required mechanical ventilation and 2 people who died. Many allergic reactions were reported as non-serious, but required interventions to treat a life-threatening event, example: epinephrine, nebulizers, albuterol, glucocorticoids, and supplemental oxygen. Two people experienced a positive rechallenge (which are allergic reactions after repeated vaccination with RIV4), including a person who despite premedication with antihistamines developed respiratory difficulties, required epinephrine, and was transported to the emergency department. The occurrence of anaphylaxis and other allergic reactions in some individuals may reflect an underlying predisposition to atopy that may manifest itself after an exposure to any drug or vaccine and does not necessarily suggest that Flublok Quadrivalent is particularly allergenic. Post marketing safety surveillance will continue to be vital for understanding the benefits and risks of quadrivalent recombinant influenza vaccine.  This case involves a 84 year old male patient who experienced weakness/progressive generalized muscle weakness/neuromuscular weakness of unknown etiology (muscular weakness), respiratory failure/acute hypoxic respiratory failure (acute respiratory failure), recurrent aspiration (aspiration), recurrent mucus plugging (bronchial secretion retention), pneumonia, gastrointestinal bleeding (gastrointestinal haemorrhage), hypertension, atrial fibrillation, possibly GBS (Guillain-Barre syndrome) and Eaton-Lambert syndrome (myasthenic syndrome) or myasthenia gravis, after he received INFLUENZA QUADRIVALENT RECOMBINANT VACCINE [FLUBLOK QIV].  Past medical treatment, vaccination family history and concomitant medications were not reported.  At the time of the event, the patient had ongoing coronary artery disease.   On an unknown date, the patient received a dose of suspect INFLUENZA QUADRIVALENT RECOMBINANT VACCINE [lot number, expiry date and other dosing details were not reported] via an unknown route at unknown administration site for prophylactic vaccination.  On an unknown date, the patient developed a serious weakness (muscular weakness) and respiratory failure (acute respiratory failure), 10 days following the administration of INFLUENZA QUADRIVALENT RECOMBINANT VACCINE. The patient was hospitalized for this event.  The hospital management included mechanical ventilation, intravenous immunoglobulin, and glucocorticoids as a corrective treatment to the patient.  It was reported that, patient's hospital course was complicated by pneumonia, hemorrhagic shock (shock haemorrhagic) due to gastrointestinal bleeding (gastrointestinal haemorrhage), hypertension, and atrial fibrillation. The medical records state that he had neuromuscular weakness of unknown etiology, possibly GBS (Guillain-Barre syndrome), Eaton-Lambert syndrome (myasthenic syndrome) or myasthenia gravis. (unknown latency)  The inpatient death summary listed, acute hypoxic respiratory failure with recurrent mucus plugging (bronchial secretion retention) and recurrent aspiration (aspiration) in the setting of progressive generalized muscle weakness. (unknow latency)  The pneumonia, shock haemorrhagic, gastrointestinal haemorrhage, atrial fibrillation, Guillain-Barre syndrome, myasthenic syndrome, myasthenia gravis, aspiration, bronchial secretion retention and aspiration were assessed as medically significant.   Details of laboratory data not reported.  It was not reported if the patient received any additional corrective treatment before death.  At the time of reporting, event outcome for pneumonia, gastrointestinal haemorrhage, shock haemorrhagic, hypertension, atrial fibrillation, Guillain-Barre syndrome and myasthenic syndrome or myasthenia gravis was not reported at the time of reporting. The muscular weakness, acute respiratory failure, aspiration and bronchial secretion retention were the events which were listed in death summery hence outcome of these events was considered as Fatal.  At the time of reporting, date of death was not reported.   It was unknown if an autopsy was done also the cause of death was clearly reported.  There will be no information available on the batch number for this case.; Sender's Comments: This case involved a 84 year old male patient who presented with muscular weakness, acute respiratory failure, aspiration, bronchial secretion retention, pneumonia, gastrointestinal haemorrhage, hypertension, atrial fibrillation, Guillain-Barre syndrome and myasthenic syndrome or myasthenia gravis after the administration of FLUBLOK QIV. Although time of onset is compatible for muscular weakness and acute respiratory failure, concurrently present Lambert Eaton Syndrome and gastrointestinal hemorrhage may indicate complications of existing comorbidities offering potential alternative etiology. At the time of reporting patient had ongoing coronary artery disease.  Muscular weakness, acute respiratory failure, aspiration and bronchial secretion retention were the events which listed in death summery. Moreover, information regarding previous vaccination/medical treatment and tolerance, concomitant medications, other additional underlying risk factors if any and their etiological factors, autopsy result and laboratory investigations results, would be needed for further assessment of the case. Based on reported information role of suspect vaccine cannot be assessed.; Reported Cause(s) of Death: weakness/progressive generalized muscle weakness/neuromuscular weakness of unknown etiology; respiratory failure/acute hypoxic respiratory failure; recurrent aspiration; recurrent mucus plugging