acute myocarditis; occasional shortness of breath; occasional fatigue; Covid booster; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) for a Pfizer sponsored program. The reporter is the patient.  A 70 year-old male patient received bnt162b2 (BNT162B2), administered in arm left, administration date 04Oct2021 (Lot number: 30145BA) at the age of 70 years as dose 3 (booster), single for covid-19 immunisation; influenza vaccine (INFLUENZA VACCINE), administered in arm right, administration date 04Oct2021 (Batch/Lot number: unknown) as dose 1, single. Relevant medical history included: "Lymphoma" (unspecified if ongoing), notes: Had chemotherapy CHOP-R. It was 16 Years ago. There were no concomitant medications. Vaccination history included: Bnt162b2 (First dose, Date: 12Feb2021, Lot: EL8982, Exp: Unknown , Site: Thinks it was in the left arm , AE(s) following prior vaccinations: None.), administration date: 12Feb2021, when the patient was 69 years old, for COVID-19 Immunization, reaction(s): "None"; Bnt162b2 (Second dose, Date: 05Mar2021, Lot: EM9810, Exp: Unknown, Site: Thinks it was in the left arm, AE(s) following prior vaccinations: None.), administration date: 05Mar2021, when the patient was 69 years old, for COVID-19 Immunization, reaction(s): "None". The following information was reported: MYOCARDITIS (hospitalization, medically significant) with onset Dec2021, outcome "unknown", described as "acute myocarditis"; IMMUNISATION (medically significant) with onset 04Oct2021, outcome "unknown", described as "Covid booster"; DYSPNOEA (non-serious) with onset Nov2021, outcome "unknown", described as "occasional shortness of breath"; FATIGUE (non-serious) with onset Nov2021, outcome "unknown", described as "occasional fatigue". The patient was hospitalized for myocarditis (start date: 14Dec2021, discharge date: 16Dec2021, hospitalization duration: 3 day(s)). The events "acute myocarditis", "occasional shortness of breath" and "occasional fatigue" were evaluated at the physician office visit and emergency room visit. The patient underwent the following laboratory tests and procedures: blood test: unknown results, notes: showed something in the blood stream/he guesses when you have congestive heart failure, it throws off some drug; echocardiogram: unknown results; electrocardiogram: unknown results; magnetic resonance imaging heart: unknown results; x-ray: enlarged heart.  Clinical course: The patient sent Pfizer a letter about his experienced adverse event, and they said to call the RA to report it. The patient called about the Covid-19 vaccine and reported that he was a healthy 70-year-old male and received Covid booster and the flu vaccine on 04Oct2021. About a month later, he started experiencing occasional shortness of breath and occasional fatigue in early to middle Nov2021. The patient was admitted to the hospital in the mid Dec2021 for 3 days and his diagnosis was acute myocarditis. The patient asked was this condition related to the vaccine. The report was not related to a study or programme. Reporter seriousness for Acute myocarditis was Hospitalization. The patient was in hospital for Acute myocarditis form 14Dec2021 to 16Dec2021. The patient received Covid-19 Vaccine (Verbatim) was Covid-19 Booster. The patient received Flu Vaccine injection in the right arm on same date with the Pfizer vaccine considered as suspect. No. of Previous Doses: Yes, in the previous years. This was his first dose this flu season. The doctor did not suspect anything at the time and thought it was something else. They did a blood test showed something in the blood stream, he guessed when you have congestive heart failure, it throws off some drug, something in the blood stream, and that was present. The x-ray showed an enlarged heart, and he was told to go to the hospital by his doctor. They did an Echocardiogram, EKG, and cardiac MRI in the hospital. They put dyes on the patient to check if he had a blockage which he did not. The AE(s) shortness of breath and fatigue was diagnosed with acute Myocarditis at the hospital. The patient was hospitalized in the hospital for 3 days. Prior Vaccinations (within 4 weeks) If applicable, list any other vaccinations within four weeks prior to the first administration date of the suspect vaccine(s) was none. AE(s) following prior vaccinations was none. Family Medical History Relevant to AE(s) was none.  No follow-up attempts are possible. No further information is expected.