vaccine-associated acute myopericarditis and pneumonitis; Acute respiratory distress with oxygen desaturation; vaccine-associated acute myopericarditis and pneumonitis; This literature-non-study case was reported in a literature article and describes the occurrence of MYOCARDITIS (vaccine-associated acute myopericarditis and pneumonitis), ACUTE RESPIRATORY DISTRESS SYNDROME (Acute respiratory distress with oxygen desaturation) and PNEUMONITIS (vaccine-associated acute myopericarditis and pneumonitis) in a 21-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.       Concurrent medical conditions included Attention deficit hyperactivity disorder and Nonsmoker.    On an unknown date, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced MYOCARDITIS (vaccine-associated acute myopericarditis and pneumonitis) (seriousness criteria hospitalization and medically significant) and PNEUMONITIS (vaccine-associated acute myopericarditis and pneumonitis) (seriousness criterion hospitalization). an unknown date, the patient experienced ACUTE RESPIRATORY DISTRESS SYNDROME (Acute respiratory distress with oxygen desaturation) (seriousness criteria hospitalization and medically significant). The patient was treated with COLCHICINE for Adverse event, at an unspecified dose and frequency and PREDNISONE for Adverse event, at a dose of 40 milligram. At the time of the report, MYOCARDITIS (vaccine-associated acute myopericarditis and pneumonitis), ACUTE RESPIRATORY DISTRESS SYNDROME (Acute respiratory distress with oxygen desaturation) and PNEUMONITIS (vaccine-associated acute myopericarditis and pneumonitis) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Anti-cyclic citrullinated peptide antibody: negative (Negative) Negative. On an unknown date, Antineutrophil cytoplasmic antibody: negative (Negative) Negative. On an unknown date, Antinuclear antibody: negative (Negative) Negative (anticentromere, anti-Jo1, antinuclear ribonucleoprotein, anti-Scl 70, antismith, all were negative.). On an unknown date, Brain natriuretic peptide: 233 pg/ml (High) 233 pg/mL. On an unknown date, C-reactive protein: 159 mg/l (High) 159 mg/L. On an unknown date, Chest X-ray: bilateral lower lobe interstitial thickening Bilateral lower lobe interstitial thickening, chest x-ray antero-posterior view showing vague bibasilar ground-glass opacities with mild interstitial thickening within the lower lobes. On an unknown date, Computerised tomogram thorax: pneumonitis changes suggestive of bilateral lower lobe consolidation and inflammatory changes suggestive of pneumonitis.  No pulmonary embolism was found.Computed tomography angiography thorax showed patchy alveolar consolidation involving the central parenchyma of both lower lobes with smaller zone of alveolar opacification also seen along the posterior margin of the middle lobe. On an unknown date, DNA antibody: negative (Negative) Negative. On an unknown date, Echocardiogram: left ventricular ejection fraction of 54 left ventricular ejection fraction of 54% and normal global systolic left ventricular function. On an unknown date, Electrocardiogram: st-segment elevation (abnormal) ST-segment elevation in leads I, II, aVL, aVF, V3, V4, V5, and V6 and ST depression in leads III and V1 and no new findings Subsequent electrocardiogram did not show any new findings. On an unknown date, Histone antibody: negative (Negative) Negative. On an unknown date, Physical examination: unremarkable (normal) Unremarkable. On an unknown date, Procalcitonin: negative (Negative) Negative. On an unknown date, Red blood cell sedimentation rate: 50 mm/h (High) 50 mm/h. On an unknown date, Respiratory viral panel: negative (Negative) Negative. On an unknown date, Rheumatoid factor: negative (Negative) Negative. On an unknown date, SARS-CoV-2 test: negative (Negative) Negative. On an unknown date, Troponin: 901 ng/l (High) 901 ng/L, 1595 ng/l (High) trended upwards to 1595 ng/L and 1473 ng/l (High) plateaued at 1473 ng/L. On an unknown date, Ultrasound Doppler: negative (Negative) Negative. On an unknown date, Vital signs measurement: normal (normal) Normal and stable (normal) In the emergency department, the vital signs were stable. On an unknown date, White blood cell count: 15,400/µl (High) 15,400/µL.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered MYOCARDITIS (vaccine-associated acute myopericarditis and pneumonitis), ACUTE RESPIRATORY DISTRESS SYNDROME (Acute respiratory distress with oxygen desaturation) and PNEUMONITIS (vaccine-associated acute myopericarditis and pneumonitis) to be related.    Patient's BMI was reported as 26.6 kg/m2. No concomitant medications were reported.  Company comment: This literature-non-study case concerns a 21-year-old male patient, with no relevant medical history reported, who experienced the serious (hospitalized and medically significant)unexpected AESI of Acute respiratory distress and the serious (hospitalized) expected AESI of myocarditis and unexpected event of pneumonitis after the third dose of mRNA-1273 (reported as booster dose). The patient was hospitalized due to chest pain, shortness of breath, and 1 episode of hemoptysis, 2 days after vaccination. He complained of generalized body aches, headache, and fever. Laboratory test, ECG, echocardiogram, COVID-19 PCR (negative), Chest x-ray, and Computed tomography angiography thorax were performed. Cardiology was consulted and diagnosis acute myopericarditis. Treatment with non steroid anti-inflammatory drugs and colchicine was initiated. During his hospital course he developed acute respiratory distress with oxygen desaturation. No pulmonary embolism was found. Prednisone taper starting at a dose of 40 mg for 10 days. After 3 days with NSAIDs, colchicine, and prednisone, the patient clinically improved and was stable for discharge. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This literature-non-study case concerns a 21-year-old male patient, with no relevant medical history reported, who experienced the serious (hospitalized and medically significant)unexpected AESI of Acute respiratory distress and the serious (hospitalized) expected AESI of myocarditis and unexpected event of pneumonitis after the third dose of mRNA-1273 (reported as booster dose). The patient was hospitalized due to chest pain, shortness of breath, and 1 episode of hemoptysis, 2 days after vaccination. He complained of generalized body aches, headache, and fever. Laboratory test, ECG, echocardiogram, COVID-19 PCR (negative), Chest x-ray, and Computed tomography angiography thorax were performed. Cardiology was consulted and diagnosis acute myopericarditis. Treatment with non steroid anti-inflammatory drugs and colchicine was initiated. During his hospital course he developed acute respiratory distress with oxygen desaturation. No pulmonary embolism was found. Prednisone taper starting at a dose of 40 mg for 10 days. After 3 days with NSAIDs, colchicine, and prednisone, the patient clinically improved and was stable for discharge. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.