Hallucinating; Paranoid; Agitated; delusional; Worsened significantly after the second; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team.  A 79 year-old male patient received bnt162b2 (BNT162B2), administered in arm, administration date 02Mar2021 (Batch/Lot number: unknown) at the age of 78 years as dose 2, single for covid-19 immunisation. Relevant medical history included: "Allergies" (unspecified if ongoing); "Anca vasculitis" (unspecified if ongoing), notes: had this disease for 3 years now. Concomitant medication(s) included: RITUXIMAB taken for anti-neutrophil cytoplasmic antibody positive vasculitis. Vaccination history included: Bnt162b2 (Dose no: 1), administration date: 08Feb2021, when the patient was 78 years old, for COVID-19 immunization, reaction(s): "He was tired and slept it off".  The following information was reported: HALLUCINATION (medically significant) with onset 2021, outcome "not recovered", described as "Hallucinating"; PARANOIA (non-serious) with onset 2021, outcome "not recovered", described as "Paranoid"; AGITATION (non-serious) with onset 2021, outcome "not recovered", described as "Agitated"; DELUSIONAL PERCEPTION (non-serious) with onset 2021, outcome "not recovered", described as "delusional"; CONDITION AGGRAVATED (non-serious) with onset 2021, outcome "unknown", described as "Worsened significantly after the second". The events were evaluated at the physician office visit and emergency room visit. Therapeutic measures were taken as a result of the events.   Clinical course: He has an autoimmune disease called Anca vasculitis. This disease affects his temporal lobe, and the small blood vessel area. Oxygen doesn't get to his brain right. That affects his cognition. His symptoms look a lot like dementia. He has dementia symptoms. The autoimmune disease triggered everything after the vaccine. Patient has had this disease for 3 years now. He has a lot of symptoms from this vasculitis that make it seem like dementia. His side effect after the Pfizer Biontech COVID 19 vaccine happened a little after the vaccine and then worsened significantly after the second. At first she thought it was just his autoimmune disease but then he got better and it occurred after the booster as well. He gets extremely delusional, hallucinates, he is paranoid and agitated. It was reported that after the first vaccine there was a slight difference. They thought maybe they were just imagining it. After the first dose, he was tired and slept it off. Then he was fine. Then, when he was supposed to get the second COVID shot he had a worse reaction. In a day, he was hallucinating, paranoid, and agitated. It was horrible. He was in and out of the emergency room. The doctor ended up giving him Seroquel IC Quetiapine Fumarate which didn't help. The doctor gave him Seroquel IC Quetiapine Fumarate 25mg first. It says one tablet by mouth at bedtime. He became more agitated. Then, the doctor gave him Klonopin/Clonazepam on 07May2021, and he couldn't stand up when he took that. Both of those made him worse. His Neurologist prescribed him Aricept. At this point he is due also for his Rituximab infusion that he gets every 6 months for his vasculitis. He got his rituximab infusion in Oct2021. He did have dementia like symptoms because the oxygen is not getting to his brain right so they weren't going to send him for the third vaccine. Since nobody knows like the doctors, they decided to go ahead. He is doing so much better, and is stabilized now. Now, after the booster shot, they know it was the vaccine all along.   The lot number for bnt162b2 was not provided and will be requested during follow up.