PLATELET COUNT ABNORMAL; COMPUTERISED TOMOGRAM HEAD ABNORMAL; ANTICOAGULANT THERAPY; MECHANICAL VENTILATION; CEREBRAL VENOUS SINUS THROMBOSIS; CEREBRAL HAEMORRHAGE; MENTAL IMPAIRMENT; SEIZURE; CATASTROPHIC BRAIN DAMAGE; SUFFERING TRAGICALLY FROM A BLOOD CLOT; SEVERE HEADACHE/MIGRAINES; INCORRECT ROUTE OF DRUG ADMINISTRATION; This spontaneous report received from a health care professional via a Regulatory Authority VAERS [Vaccine Adverse Event Reporting System FDA Inbound Unit] concerned a 33 year old male of unspecified race and ethnicity. The patient's weight was 185 (unit unspecified), and height was 261.62 centimeters. The patient's concurrent conditions included: alcohol use, nonsmoker, and pistachio and cashew allergy, and other pre-existing medical conditions included: The patient was young, healthy and very athletic. The patient was in amazing health before his stroke. The patient had no illness at the time of vaccination, no past history of similar event, no adverse event after any previous vaccination, no allergy to vaccine, or drug. The patient had no pre-existing acute illness 30 days prior to vaccination, no history of hospitalization in last 30 days, with cause. The patient had no Family history of any disease (relevant to vaccination) or allergy. The patient had no history of drug abuse. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, intravenous, and batch number: 1820095, expiry: unknown) dose was not reported, 1 total administered on left (exact location unspecified) on 07-JUL-2021 for prophylactic vaccination. It was reported that the vaccine was injected to a vein (incorrect route of drug administration). On 18-JUL-2021, (10 days after receiving the vaccine) the patient experienced severe headaches (migraines) at the back of his head, to the point that he could not work for the entire week. On the same day, the patient suffered from a tragic blood clot. On 24-JUL-2021, the patient visited general practitioner who prescribed a magnetic resonance imaging (MRI), pain reliever, and muscle relaxant. On 24-JUL-2021, the patient experienced a seizure at home and he was rushed to the emergency room (ER), and admitted to the hospital; where he suffered a massive stroke in his sinus which led to bleeding and the doctors diagnosed as catastrophic brain damage. On the same day, the patient also had cerebral venous sinus thrombosis, cerebral haemorrhage, anticoagulant therapy, computerised tomogram head abnormal, mechanical ventilation, mental impairment. On imaging, he was found to have extensive dural venous sinus thrombosis with hemorrhage. He was treated with anticoagulation, anti-seizure medication, invasive mechanical ventilation, and transferred to alternated hospital for consideration of endovascular treatment. On an unknown date, the patient had a craniotomy and surgery to remove the clot. It was reported that the patient was currently on life support. The doctors had tested his blood for any other blood disorders or potential culprits for a stroke, but none had been found. His platelet levels had led them to conclude that this was caused by the J&J vaccine (platelet count abnormal). Laboratory data included: Head computerised tomogram (CT), there was near occlusive dural venous sinus thrombosis in the superior sagittal sinus torcular and right transverse sinus as well as some right-sided cortical veins at the vertex. There was a sizeable parenchymal hemorrhage centered in the high right frontal lobe as above, compatible with hemorrhagic venous infarct in this context. There was no evidence of large vessel occlusion, high-grade stenosis, aneurysm involving the intracranial arteries. On 28-JUL-2021, Laboratory data included, MRI that confirmed patient had a hemorrhagic stroke. Laboratory data (dates unspecified) included: Blood test (NR: not provided) Not reported, and Platelet count (NR: not provided) Not reported. On 17-Aug-2021, the patient continued in the hospital and was kept alive via breathing and feeding tubes. The patient had exhibited some eye movement but was unable to communicate. The patient's sister stated he had suffered severe brain damage. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from severe headache/migraines, seizure, catastrophic brain damage, and suffering tragically from a blood clot, and the outcome of cerebral haemorrhage, cerebral venous sinus thrombosis, computerised tomogram head abnormal, mental impairment, anticoagulant therapy, mechanical ventilation, platelet count abnormal and incorrect route of drug administration was not reported. This report was serious (Hospitalization Caused / Prolonged, and Other Medically Important Condition). This case, involving the same patient is linked to 20210763386.  Additional information was received from a health care professional on 01-OCT-2021. It was determined that Manufacturer Case Number 20210763386 was a duplicate of this case. All relevant information regarding this case will be submitted under Manufacturer Case Number 20210813051. Added patient's demographics (initials, height, weight, age at the time of vaccination), pre-existing and concurrent conditions, new events (blood clot, catastrophic brain damage, seizure, severe headache, incorrect route of drug administration and platelet count abnormal), lab tests. Updated therapy start date, route of administration, vaccination site, batch number.; Sender's Comments: V1: 20210813051-COVID-19 VACCINE AD26.COV2.S-Catastrophic brain damage, suffering tragically from a blood clot, platelet count abnormal. Follow-up received regarding Clinical Details. 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). This spontaneous report received from a health care professional via VAERS concerning a 33-year-old male of unspecified race who experienced Cerebral venous sinus thrombosis and Cerebral hemorrhage 16 days post vaccination. As of this report, Patient's height , weight, and concomitant medications  were not reported. The patient had  no relevant past medical history . Sixteen days post vaccination the patient presented to the hospital with recurrent seizure and declining mental status after persistent headache for previous several days. On imaging, he was found to have extensive Dural venous sinus thrombosis with hemorrhage. No platelet count was provided. He was treated with unspecified anticoagulation, anti-seizure medication, invasive mechanical ventilation, and transferred to alternated hospital for consideration of endovascular treatment. Head computerized tomogram (CT) shows near occlusive Dural venous sinus thrombosis in the superior sagittal sinus torcular and right transverse sinus as well as some right-sided cortical veins at the vertex. There is a sizeable parenchymal hemorrhage centered in the high right frontal lobe ,compatible with hemorrhagic venous infarct.  Information is limited in this case, and the occurrence of Cerebral venous sinus thrombosis and Cerebral hemorrhage could represent background incidence of such events in the general population. However, a relationship with Janssen Covid-19 vaccine cannot be ruled out and thus the relationship is considered indeterminate.