Brain fog, usually when you kind of feel sluggish like you had a concussion or stroke; Brain fog, usually when you kind of feel sluggish like you had a concussion or stroke; high altitude sickness like less oxygen in the brain you just feel kind of gazed or confused; high altitude sickness like less oxygen in the brain you just feel kind of gazed or confused; Brain fog, usually when you kind of feel sluggish like you had a concussion or stroke; Brain fog, usually when you kind of feel sluggish like you had a concussion or stroke; high altitude sickness like less oxygen in the brain you just feel kind of gazed or confused; then you have to lay in bed and deal with vertigo until you; tiredness/extremely tired; went to sleep for 8 hours; This is a spontaneous report from a contactable Nurse, reported for a patient (Second Family member). A patient of unspecified age and gender received BNT162B2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE; Formulation: Solution for injection; Batch/lot number and Expiration date : Unknown), via an unspecified route of administration on an unspecified date as dose number unknown, for COVID-19 immunisation. The patient medical history was not reported and concomitant medications included Testosterone 5 gm, 1% (Dosage were not appropriately clarified), taken for unspecified indication and unknown if ongoing. Other medication and medical conditions: born with extra female chromosome. (was born with XXY chromosome so I have under 200 testosterone, 30 estrogen and my body doesn't produce hormones like other peoples or 'approach systems' (Further clarification was unknown). On an unspecified date, the patient experienced brain fog for about 2 and a half months, usually when you kind of feel sluggish like you had a concussion or stroke or high altitude sickness like less oxygen in the brain you just feel kind of gazed or confused or you feel extremely tired/ Tiredness. Had tiredness, went to sleep for 8 hours, wake up for 2 or 3 hours, and had some coffee, then were really tired, then had to lay in bed and deal with vertigo until you (incomplete sentence)." Reporter stated that "only thing I have, that doesn't make me normal is I am born with extra female chromosome. I have been XXY chromosome variant so the men are born with XY women are born with XX chromosomes. I was born with XXY chromosome so I have under 200 testosterone, 30 estrogen and my body doesn't produce hormones like other peoples or 'approach systems' (Further clarification was unknown. Reporter stated that while on Pfizer for the both terms of taking the dosage (Further clarification was unknown), patient was taking Testosterone 5 gm, 1% Testosterone (Dosage were not appropriately clarified), a gel on both arms but then after about 2 weeks of taking it (Testosterone), after the second dosage patient started feeling dizzy. Reporter had tiredness, went to sleep for 8 hours, wake up for 2 or 3 hours, and get some coffee, then are really tired, then you have to lay in bed and deal with vertigo. Clinical outcome of events was unknown.  Information on lot/ batch number has been requested.; Sender's Comments: Based on known drug safety profile, there is reasonable possibility of causal association between the event Intellectual disability, Cerebrovascular accident and the suspect drug BNT162B2 . The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.