ENCEPHALOPATHY; SEIZURE; ACUTE HEPATITIS; PHOTOPHOBIA; CHILLS; FEVER; This spontaneous report was received from literature. This report concerned a 21 year old female. The objective of this case report study was to describe Multisystem Inflammatory Syndrome in Children and Adolescents (MIS-C) in a young adult with recent vaccination. The patient's height, and weight were not reported. The patient's past medical history included: asymptomatic COVID infection, and concurrent conditions included: asthma. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: Unknown) dose was not reported, 1 total, start therapy date was not reported for prophylactic vaccination. The batch number was not reported and has been requested. No concomitant medications were reported. On an unspecified date, two weeks after vaccination, the patient was presented to the emergency department (ED) with fevers, chills and photophobia. On evaluation, COVID test was negative. Labs were notable for leukopenia, elevated liver enzymes. The patient was admitted to the medical floor. Date of hospitalization was not reported. The patient's course was complicated by worsening transaminases greater than 2000 IU/L with progressive encephalopathy. The patient had witnessed seizure activity requiring intubation and transfer to the Intensive Care Unit (ICU). Laboratory data included: Computed Tomography (CT) abdomen was unremarkable. Head CT showed no acute abnormalities. Brain Magnetic Resonance Imaging (MRI) showed diffuse nonspecific white matter signal abnormalities. Additional lab work revealed ferritin of 937 mcg/L, and CRP of 47.3 mg/L and an elevated NT-proBNP. Film array and hepatitis panel was negative. COVID spike and nucleocapsid antibodies were both positive. The patient underwent a liver biopsy which was consistent with acute hepatitis and bone marrow biopsy which was negative for Hemophagocytic lymphohistiocytosis (HLH). Lumbar puncture with elevated opening pressure of 27 cm H20. Extensive infectious workup for bacterial, fungal and viral etiologies were negative. The patient met criteria and was diagnosed with Multisystem Inflammatory Syndrome in Children and Adolescents. The patient received high dose Intravenous Dexamethasone, Intravenous Immunoglobulin (IVIG) and anakinra infusion. The lab work and encephalopathy improved and patient was discharged home. Date of discharge and number of days hospitalized was not reported. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient was recovering from multisystem inflammatory syndrome in children and adolescents (MIS-C) in a young adult. The authors concluded that it was currently unknown if Multisystem Inflammatory Syndrome in Children and Adolescents might follow COVID immunization, but a need exists to define this potential entity for monitoring as a potential adverse event. It is also important to maintain an index of suspicion for this disorder. This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0: This spontaneous report received from literature concerned a 21-year-old female who experienced multisystem inflammatory syndrome 14 days after vaccination. Medical history includes asthma. Concomitant medications were not reported. The patient presented to the emergency department 2 weeks after vaccine with fever, chills, and photophobia. Initial labs showed leukopenia, elevated liver enzymes and the patient was admitted to the medical floor. The clinical course was complicated by elevated transaminases (>2000 IU/L), progressive encephalopathy and seizure activity requiring intubation and transfer to the intensive care unit. Additional labs include ferritin 937 mcg/L, and CRP of 47.3 mg/L, pro-BNP high, hepatitis panel negative, and a negative COVID test (unspecified type). COVID spike and nucleocapsid antibodies were positive. MRI brain showed diffuse nonspecific white matter abnormalities. Liver biopsy showed acute hepatitis, and Bone marrow biopsy was negative for hemophagocytic lymphohistiocytosis. Extensive workup for bacterial, fungal, and viral etiologies was negative and criteria for multisystem inflammatory syndrome in children and adolescents was met. The patient's condition improved and was discharged home after treatment with high dose dexamethasone, IVIG, and anakinra infusion. A recent asymptomatic COVID-19 infection (indicated by positive nucleocapsid antibodies) may have increased the risk for the event to occur. However, considering the temporal relationship with vaccination, a relationship with Janssen Covid-19 vaccine cannot be ruled out. Therefore, the relationship is considered indeterminate.