HORRIBLE SEIZURE; TIREDNESS; MEMORY LOSS; HIGH BLOOD  PRESSURE; FELT REALLY SICK/ GENERALLY FEELING UNWELL SINCE SEIZURE OCCURRED; NASUEATED; THREW UP; SLEPT FOR 2 DAYS/SLEEPS A LOT; DID NOT EAT; This spontaneous report received from a consumer concerned a 64 year old male of unknown race and ethnicity. The patient's height, and weight were not reported. The patient's concurrent conditions included heartburn, alcohol use, and cigarette smoker, and other pre-existing medical conditions included, the patient did not have any known allergy and did not have history of drug abuse and illicit drug use. 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 administered on JUN-2021 for prophylactic vaccination. The batch number was not reported and has been requested. Concomitant medications included lansoprazole for heartburn.  On an unspecified date, in JUN-2021, the patient, felt really sick for 48 hours after receiving the vaccine and patient felt nauseated, threw up, slept for 2 days and did not eat. On 19-SEP-2021, the patient experienced horrible seizure which lasted for 3 to 4 minutes. The reporter reported that this was the first time the patient had experienced a seizure ever in his life. The reporter called 911 and ambulance arrived in response to the seizure. The patient was taken by ambulance to a small Emergency medical service station (EMS) and since there was no hospital close enough. The patient was then air lifted to another hospital where he was admitted to hospital on 19-Sep-2021. The patient blood pressure was really high for a bit during transport by emergency services, but exact blood pressure value was not provided. On 19-Sep-2021 two brain Computerized tomogram (CT scans) were performed which showed negative results and no tissue damage. 20-SEP-2021 patient underwent Electroencephalography (EEG) and on 21-SEP-2021 Magnetic resonance imaging (MRI) on brain done which did not show anything everything was clear. The patient was in hospital from 19-Sep-2021 until 22-Sep-2021. While in hospital the patient had chest x-rays, heart monitor, oxygen, bloodwork which shows nothing, also patient had intravenous treatment. The reporter reported that the type of seizure was not classified by the doctor but the she thought it was grand mal seizure. The patient continues to feel unwell after the seizure occurred and continues to experience ongoing memory loss, ongoing tiredness, and sleeps a lot. The reporter reported that no new cleaning products were brought into the home, eating habits and general habits have not changed. The patient was taking vitamin B1 and levetiracetam 500mg 1 tablet twice daily since the seizure occurred. Patient admitted in hospital for 3 days. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient recovered from did not eat, nauseated, and threw up on JUN-2021, and high blood pressure on 19-SEP-2021, and had not recovered from slept for 2 days/sleeps a lot, memory loss, tiredness, felt really sick/ generally feeling unwell since seizure occurred, and horrible seizure. This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0: 20210950659-Covid-19 vaccine ad26.cov2.s-Horrible seizure. 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).