massive seizure; booster; Vertigo; Phenobarbital level was low; arms hurting; clot on her brain; Unconscious; split her head open/had nine staples to her head; fell on the floor; concussion; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) for a Pfizer sponsored program. The reporter is the patient.  A 75 year-old female patient received bnt162b2 (BNT162B2), administered in arm left, administration date 23Aug2021 (Lot number: FC3181) at the age of 75 years as dose 3 (booster), single for covid-19 immunisation; phenobarbital (PHENOBARBITAL) (ongoing) (Batch/Lot number: unknown) at 120 mg daily (every night in the evening) for epilepsy. Relevant medical history included: "epileptic" (ongoing), notes: she has been epileptic since she was younger, but they discovered at age 14. There were no concomitant medications. Past drug history included: Dilantin for epileptic, notes: when she was younger,  in an amber orange colored bottle. Vaccination history included: Bnt162b2 (dose 1; lot number: ET1685 or EI1685), administration date: 11Jan2021, when the patient was 74 years old, for Covid-19 immunization; Bnt162b2 (dose 2; lot number: EL9262), administration date: 01Feb2021, when the patient was 74 years old, for Covid-19 immunization. The following information was reported: IMMUNISATION (hospitalization) with onset 23Aug2021, outcome "unknown", described as "booster"; SEIZURE (hospitalization, medically significant) with onset 31Oct2021 19:00, outcome "recovered with sequelae", described as "massive seizure"; CEREBRAL THROMBOSIS (medically significant) with onset 31Oct2021, outcome "recovered", described as "clot on her brain"; LOSS OF CONSCIOUSNESS (medically significant) with onset 31Oct2021, outcome "recovered with sequelae" (01Nov2021), described as "Unconscious"; HEAD INJURY (medically significant) with onset 31Oct2021, outcome "recovered with sequelae" (30Nov2021), described as "split her head open/had nine staples to her head"; FALL (non-serious) with onset 31Oct2021, outcome "recovering", described as "fell on the floor"; CONCUSSION (non-serious) with onset 31Oct2021, outcome "recovering", described as "concussion"; VERTIGO (non-serious) with onset 01Nov2021, outcome "recovering", described as "Vertigo"; ANTICONVULSANT DRUG LEVEL BELOW THERAPEUTIC (non-serious) with onset 31Oct2021, outcome "recovered with sequelae", described as "Phenobarbital level was low"; PAIN IN EXTREMITY (non-serious) with onset 31Oct2021, outcome "recovering", described as "arms hurting". The patient was hospitalized for immunisation, seizure (start date: 01Nov2021, discharge date: 02Nov2021, hospitalization duration: 1 day(s)). The events "massive seizure" and "phenobarbital level was low" were evaluated at the physician office visit. The patient had been taking Phenobarbital. Her Phenobarbital level was very low, and she had a massive seizure after the booster shot. The massive seizure was in the evening about 19:00. She fell on the floor and split her head open, had 9 staples, a concussion and a clot on her brain all from the floor. Stated that she was on the floor for 16 hours because she lived alone. Stated that the seizure lasted for a minute, but she did not know because she was unconscious. She recovered from having her head split open when they took the staples out but had lasting effects of vertigo. Stated that she was unconscious for 16 hours and has lasting effect of vertigo and arms hurting. Stated that on 01Nov2021 her phenobarbital was 11. Stated that the doctor increased her phenobarbital. Stated that she had it tested shortly after they increased it and her phenobarbital is 30. Increased her Phenobarbital from 120mg every night in the evening to 60mg in the morning and 120 mg at night from 01Nov2021. She had lasting effects of her level being low such as vertigo and the concussion. The patient had been taking meclizine for vertigo. The patient underwent the following laboratory tests and procedures: computerised tomogram: the clot did not get bigger so they left it alone, notes: had four CAT scans, they told her if the clot got bigger that they would have to do brain surgery and they did not have to. The action taken for phenobarbital was dosage increased. Therapeutic measures were taken as a result of seizure, head injury, vertigo, anticonvulsant drug level below therapeutic. No follow-up attempts are possible. No further information is expected.