Most of the symptoms of Myocarditis; Irregular heart rates; Tachycardia; SOB with no exertion; Fever spikes; Chest pain; Ankle swelling; Dose received 3; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 54 year-old female patient (not pregnant) received bnt162b2 (PFIZER BIONTECH COVID-19 VACCINE), administered in arm left, administration date 02Dec2021 10:00 (Lot number: EJ8762) at the age of 54 years as dose 3 (booster), single for covid-19 immunisation. Relevant medical history included: "Congenital Heart Disease" (unspecified if ongoing), notes: (take Lasix, Toprol, Lisinopril for Congenital Heart Disease); "Post Acute Covid Syndrome" (unspecified if ongoing); "Risks for Heart Disease" (unspecified if ongoing); "s/p childhood heart surgery" (unspecified if ongoing); "Severe apnea (treated)" (unspecified if ongoing); "SVT" (unspecified if ongoing); "Known allergies: Only seasonal allergies" (unspecified if ongoing); "COVID Alpha variant", start date: Nov2020 (unspecified if ongoing); "POTS" (unspecified if ongoing); "Autonomic Dysfunction" (unspecified if ongoing); "pulmonary rehab" (unspecified if ongoing). Concomitant medication(s) included: LASIX [FUROSEMIDE] taken for heart disease congenital (ongoing); TOPROL taken for heart disease congenital (ongoing); LISINOPRIL [LISINOPRIL DIHYDRATE] taken for heart disease congenital (ongoing). The patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. Vaccination history included: Bnt162b2 (Dose Number: 2, Batch/Lot No: EP7533, Location of injection: Arm Left), administration date: 03Apr2021, when the patient was 54 years old, for COVID-19 immunization; Bnt162b2 (Dose Number: 1, lot number: EN 6204, Location of injection: Arm Left, administered on 06Dec2021 (as reported)), for COVID-19 immunization. The following information was reported: IMMUNISATION (medically significant) with onset 02Dec2021, outcome "unknown", described as "Dose received 3"; MYOCARDITIS (medically significant) with onset 09Dec2021, outcome "not recovered", described as "Most of the symptoms of Myocarditis"; HEART RATE IRREGULAR (medically significant) with onset 09Dec2021, outcome "not recovered", described as "Irregular heart rates"; TACHYCARDIA (medically significant) with onset 09Dec2021, outcome "not recovered", described as "Tachycardia"; DYSPNOEA (medically significant) with onset 09Dec2021, outcome "not recovered", described as "SOB with no exertion"; PYREXIA (medically significant) with onset 09Dec2021, outcome "not recovered", described as "Fever spikes"; CHEST PAIN (non-serious) with onset 09Dec2021, outcome "not recovered", described as "Chest pain"; JOINT SWELLING (non-serious) with onset 09Dec2021, outcome "not recovered", described as "Ankle swelling". The events "most of the symptoms of myocarditis", "irregular heart rates", "tachycardia", "sob with no exertion", "fever spikes", "chest pain" and "ankle swelling" were evaluated at the physician office visit. The patient underwent the following laboratory tests and procedures: heart rate: (09Dec2021) irregular; sars-cov-2 test: (15Dec2021) negative, notes: Nasal Swab. It was unknown if therapeutic measures were taken as a result of myocarditis, heart rate irregular, tachycardia, dyspnoea, pyrexia, chest pain, joint swelling. Clinical course: Patient was a Covid Long Hauler. Patient was diagnosed with Alpha variant in Nov2020, before any treatments or Vaccines existed. Patient was still symptomatic with Autonomic Dysfunction and symptoms of POTS (Postural orthostatic tachycardia syndrome). After the 3rd vaccine, patient felt "cured" for one week- then "crashed." Patient  presumed that she was having a Long Covid relapse, but later discovered that she had most of the symptoms of Myocarditis. Irregular heart rates, tachycardia, SOB (shortness of breath) with no exertion, fever spikes- all Myocarditis symptoms except for Chest pain or ankle swelling (Patient takes LASIX, TOPROL, Lisinopril for Congenital Heart Disease). It was only today that he/she reached out to his/her MD and Cardiologist. Symptoms began 09Dec2021. Patient has missed 5 days of daily pulmonary rehab. If her symptoms continue, patient will try to get an EKG, CXR and labs on 18Dec2021. Patient called 2 doctors but could not be seen on 17Dec2021. Patient has also requested a heart monitor to wear at home from her Cardiologist. Events were reported as non-serious, results in death: no, seriousness criteria-life threatening: no, prolonged hospitalization: no, disabling/incapacitating: no, congenital anomaly/birth defect: no.    No follow-up attempts are possible. No further information is expected.