lost consciousness; incoherent; dizzy; Right Atrial Enlargement; fever; nausea; headache; Booster; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient. A 14-year-old male patient received BNT162B2 (PFIZER-BIONTECH COVID-19 MRNA VACCINE) administered in arm right, administration date 09Jan2022 13:30 (Lot number: 33025BD) at the age of 14 years as dose 3 (booster), single for covid-19 immunisation. The facility where the most recent COVID-19 vaccine was administered was Pharmacy or Drug Store. Relevant medical history included: "Asthma" (unspecified if ongoing); "Allergies" (unspecified if ongoing); "Known allergies: Latex" (unspecified if ongoing). Concomitant medications included: levocetirizine dihydrochloride (XYZAL); fluoxetine hydrochloride (PROZAC) 20 mg; VITAMIN D NOS. The patient did not receive any other vaccine within 4 weeks prior to the vaccine. Vaccination history included: Bnt162b2 (Dose Number: 2, Batch/Lot No: EW0196, Location of injection: Arm Right), administration date: 12Jun2021, when the patient was 13 years old, for COVID-19 Immunization; Bnt162b2 (Dose Number: 1, Batch/Lot No: EW0187, Location of injection: Arm Right), administration date: 22May2021, when the patient was 13 years old, for COVID-19 Immunization. The following information was reported: IMMUNISATION (medically significant) with onset 09Jan2022 13:30, outcome "unknown", described as "Booster"; LOSS OF CONSCIOUSNESS (medically significant) with onset 10Jan2022 09:00, outcome "not recovered", described as "lost consciousness"; INCOHERENT (medically significant) with onset 10Jan2022 09:00, outcome "not recovered", described as "incoherent"; DIZZINESS (medically significant) with onset 10Jan2022 09:00, outcome "not recovered", described as "dizzy"; RIGHT ATRIAL ENLARGEMENT (medically significant) with onset 10Jan2022 09:00, outcome "not recovered", described as "Right Atrial Enlargement"; PYREXIA (non-serious) with onset 10Jan2022 09:00, outcome "not recovered", described as "fever"; NAUSEA (non-serious) with onset 10Jan2022 09:00, outcome "not recovered", described as "nausea"; HEADACHE (non-serious) with onset 10Jan2022 09:00, outcome "not recovered", described as "headache".  The events "lost consciousness", "incoherent", "dizzy", "right atrial enlargement", "fever", "nausea" and "headache" were evaluated at the emergency room visit.  The patient underwent the following laboratory tests and procedures: electrocardiogram (EKG): (10Jan2022) was indicative of right atrial enlargement; COVID Nasal Swab: (10Jan2022) negative. Therapeutic measures were not taken as a result of loss of consciousness, incoherent, dizziness, right atrial enlargement, fever, nausea and headache. Prior to the vaccination, the patient was not diagnosed with COVID-19.  It was also reported that since the vaccination, the patient had been tested for COVID-19. Clinical course: Patient was at school and lost consciousness, was incoherent, dizzy and needed to be wheeled to the nurse for dismissal. Urgent Care diagnosis from EKG was indicative of Right Atrial Enlargement. Scheduled a Cardiology Appointment for this Thursday at 3PM. Has accompanying fever, dizziness, and nausea and headache as well