Death; Angiogram cerebral abnormal; Computerised tomogram head abnormal; Echocardiogram abnormal; Laboratory test; Multiple organ dysfunction syndrome; Acute hepatic failure; Acute left ventricular failure; Brain death; Brain oedema; Brain herniation; Cardiogenic shock; Cardiac failure; Pupil fixed; Distributive shock; Respiratory distress; Lactic acidosis; Intracranial pressure increased; Gastrointestinal haemorrhage; Haematemesis; Hyperammonaemia; Endotracheal intubation; Hyperventilation; Intensive care; Mental status changes; This spontaneous report received from a health care professional via a Regulatory Authority VAERS (Vaccine Adverse Event Reporting System) (VAERS ID: 1582506) and from a medical examiner concerned a 24 year old female. The patient's height, and weight were not reported. The patient's past medical history included: C-section (cesarean section), and post partum (27-FEB-2021). The patient had no allergies to medication, food or other products. The patient had no chronic or long-standing health conditions and was not pregnant at the time of vaccination. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, intramuscular, batch number: 207A21A and expiry: unknown) dose was not reported, 1 total, administered on 09-JUL-2021 to left arm for prophylactic vaccination. Concomitant medications included ferrous sulfate for unknown indication.  On 15-JUL-2021, (as reported after getting vaccinated) the patient was admitted to a local hospital and then transferred to another hospital and was finally transferred to a final medical center intensive care unit (ICU). She was admitted as a transfer from a Health Care Facilities (HCF) with acute liver failure of unknown etiology and without hepatic coma. On arrival, she had altered mental status with respiratory distress and coffee ground emesis (haematemesis). She was promptly intubated (endotracheal intubation) for airway protection. A gastrointestinal (GI) bleed (gastrointestinal haemorrhage) was suspected thus she was started on octreotide and Protonix (pantoprazole sodium) and intravenous (IV) ceftriaxone. An a-line dialysis line and an orogastric tube was placed and there was no acute GI bleeding thereafter.  Laboratory tests demonstrated severe lactic acidosis, severe hyperammonemia, and acute renal failure. Thus, Continuous Veno-Venous Hemofiltration (CVVH) was initiated. She was maxed out on triple pressor support for multifactorial vasodilatory (distributive shock) and cardiogenic shock. She had multiple organ dysfunction syndrome. Cardiac echo demonstrated acute systolic and diastolic heart failure (acute left ventricular failure and cardiac failure) with reduced ejection fraction (EF). However, no intervention was recommended by cardiology due to multiorgan failure. Computerized tomography (CT) brain on 15-JUL-2021, demonstrated diffuse brain edema (brain oedema) and mild cerebellar tonsillar herniation (brain herniation). Neurosurgery was consulted and bolt placement was performed. Increased intracranial pressures (ICPs) were consistently elevated greater than 100s. Repeat Computerized tomography (CT) brain demonstrated worsening cerebral edema (brain oedema) and herniation. By the evening of 15-JUL-2021 her pupillary exam became fixed (pupil fixed) and dilated despite being on maximum pentobarbital therapy and propofol. To decrease intracranial pressure (ICP) head of bed was at 45 degrees plus. All times mannitol and mild hyperventilation was given for cerebral edema and elevated intracranial pressure (ICPs). Once CVVH was initiated though mannitol and hypertonic saline were not treatment options as the continuous Veno-Venous Hemofiltration (CVVH) cleared the medication quickly. The patient was listed for orthotopic liver transplantation (OLT) that afternoon, but later determined not to be a candidate due to her worsening neurological status. She had a change in pupil examination, which was suggestive of worsened herniation. Her pupils became fixed dilated and CT confirmed worsening herniation. ICPs remained 120 plus despite triple pressure support in effort to maintain Cerebral perfusion pressure (CPP). A diagnostic cerebral angiogram was performed on 16-JUL-2021, due to limited ability to assess brain death secondary to medication therapy. This revealed no intracranial blood flow. After a discussion with family the patient became do not resuscitate (DNR). The family elected to discontinue supportive measures on 18-JUL-2021, and the patient was pronounced dead at 09:22.  It was reported that the patient had not recovered from the adverse events at the time of death. It was unknown if an autopsy was performed. The action taken with Covid-19 vaccine ad26.cov2.s was not applicable. The patient died due to multiple organ dysfunction syndrome, acute hepatic failure, acute left ventricular failure, brain death, brain oedema, brain herniation, cardiogenic shock, cardiac failure, pupil fixed, distributive shock, respiratory distress, lactic acidosis, intracranial pressure increased, gastrointestinal haemorrhage, haematemesis, hyperammonaemia, endotracheal intubation, hyperventilation, intensive care, mental status changes, angiogram cerebral abnormal, computerised tomogram head abnormal, echocardiogram abnormal and laboratory test on 18-JUL-2021. The cause of death on the death certificate was mentioned as cerebellar tonsillar herniation, acute liver failure, multi-organ failure and the manner of death was natural death.  This report was serious (Death).  Additional information was received from a medical examiner on 29-NOV-2021. The following information was updated and incorporated into the case narrative: The cause of death on the death certificate was mentioned as cerebellar tonsillar herniation, acute liver failure, multi-organ failure and the manner of death was natural death.; Sender's Comments: V4: Additional information received updates the cause of death on the death certificate was mentioned as cerebellar tonsillar herniation, acute liver failure, multi-organ failure and the manner of death was natural death. This updated information does not alter prior causality assessment of reported events. 20210857040-Covid-19 vaccine ad26.cov2.s -Death, Multiple organ dysfunction syndrome, Acute hepatic failure, acute left ventricular failure, Brain death, brain oedema, Brain herniation, cardiogenic shock, Cardiac failure, pupil fixed, Distributive shock, respiratory distress, Lactic acidosis, intracranial pressure increased, gastrointestinal haemorrhage, haematemesis, , hyperammonaemia, endotracheal intubation, hyperventilation, intensive care, mental status changes, angiogram cerebral abnormal, computerised tomogram head abnormal, echocardiogram abnormal, laboratory test. This event(s) is considered unassessable. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s).; Reported Cause(s) of Death: CEREBELLAR TONSILLAR HERNIATION; ACUTE LIVER FAILURE; MULTI-ORGAN FAILURE; NATURAL DEATH