Adult-onset Still's disease; Acute hypoxic respiratory failure; suspected community acquired pneumonia; This literature-non-study case was reported in a literature article and describes the occurrence of STILL'S DISEASE (Adult-onset Still's disease), ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure) and PNEUMONIA (suspected community acquired pneumonia) in a 45-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.       The patient's past medical history included Community acquired pneumonia. Concomitant products included ACETAMINOPHEN for an unknown indication.   On an unknown date, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On an unknown date, received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient experienced STILL'S DISEASE (Adult-onset Still's disease) (seriousness criteria hospitalization and medically significant), ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure) (seriousness criteria hospitalization and medically significant) and PNEUMONIA (suspected community acquired pneumonia) (seriousness criteria hospitalization and medically significant). The patient was treated with PREDNISONE for Adverse event, at a dose of 60 milligram once a day. At the time of the report, STILL'S DISEASE (Adult-onset Still's disease) outcome was unknown and ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure) and PNEUMONIA (suspected community acquired pneumonia) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Anti-cyclic citrullinated peptide antibody: negative igg (Negative) IgG, negative. On an unknown date, Antinuclear antibody: negative (Negative) negative. On an unknown date, Body temperature: 38o3°c (High) 38o3°C, at 5 days after the second dose of the vaccine, =39°c (High) O=39°C, on admission to hospital, and on daily basis and =39°c (High) =39°C, After 6 days in the hospital. On an unknown date, C-reactive protein (0o0-1o8): 27o7 mg/dl (High) 27o7 mg/dL, On admission, hospital day 1, 277o8 mg/dl (High) 277o8 mg/dL, On hospital transfer, hospital day 6, 154o8 mg/dl (High) 154o8 mg/dL,  3 days after  treatment initiation, hospital day 12 and 2o1 mg/dl (High) 2o1 mg/dL, at follow-up (2 weeks of treatment). On an unknown date, Chest X-ray: no pulmonary embolus (normal) no pulmonary embolus. On an unknown date, Computerised tomogram: left supraclavicular lymphadenopathy (abnormal) left supraclavicular lymphadenopathy on neck. On an unknown date, Haemoglobin (11o2-15o7): 10o3 ×10^9/l (Low) 10o3 ×10^9/L, On admission, hospital day 1, 11o0 ×10^9/l (Low) 11o0×10^9/L, On hospital transfer, hospital day 6, 7o9 ×10^9/l (Low) 7o9 ×10^9/L, 3 days after  treatment initiation, hospital day 12 and 9o7 ×10^9/l (Low) 9o7 ×10^9/L, At follow-up (2 weeks of treatment). On an unknown date, Lymphocyte count: 1o3 ×10 thousand cells per microlitre (abnormal) 1o3 ×10 thousand cells per microlitre, On admission, hospital day 1, 1o9 ×10 thousand cells per microlitre (abnormal) 1o9 ×10 thousand cells per microlitre, On hospital transfer, hospital day 6 and 3o0 ×10 thousand cells per microlitre (abnormal) 3o0 ×10 thousand cells per microlitre, at follow-up (2 weeks of treatment). On an unknown date, Magnetic resonance imaging: left supraclavicular lymphadenopathy (abnormal) left supraclavicular lymphadenopathy on neck. On an unknown date, N-terminal prohormone brain natriuretic peptide (0-125): 1815 pg/ml (High) 1815 pg/mL. On an unknown date, Neutrophil count: 19o6 ×10 thousand cells per microlitre (abnormal) 19o6 ×10 thousand cells per microlitre, On admission, hospital day 1, 26o5×10 thousand cells per microlitre (abnormal) 26o5×10 thousand cells per microlitre, On hospital transfer, hospital day 6 and 17o1×10 thousand cells per microlitre (abnormal) 17o1×10 thousand cells per microlitre, at follow-up (2 weeks of treatment). On an unknown date, Platelet count (150-400): 346 ×10 thousand cells per microlitre (normal) 346 ×10 thousand cells per microlitre, On admission, hospital day 1, 494 ×10 thousand cells per microlitre (High) 494 ×10 thousand cells per microlitre, On hospital transfer, hospital day 6, 1088 ×10 thousand cells per microlitre (High) 1088 ×10 thousand cells per microlitre, 3 days after  treatment initiation, hospital day 12 and 649 ×10 thousand cells per microlitre (High) 649 ×10 thousand cells per microlitre, at follow-up (2 weeks of treatment). On an unknown date, Red blood cell sedimentation rate (0-20): 85 mm/h (High) 85 mm/h. On an unknown date, Rheumatoid factor: negative (Negative) negative. On an unknown date, SARS-CoV-2 test: negative (Negative) negative; repeated COVID-19  nasopharyngeal PCR testing. On an unknown date, Serum ferritin (8-252): 2911 ng/ml (High) 2911 ng/mL, On admission, hospital day 1, 14375 ng/ml (High) 14375 ng/mL, On hospital transfer, hospital day 6, 1523 ng/ml (High) 1523 ng/mL, 3 days after  treatment initiation, hospital day 12 and 160 ng/ml (High) 160 ng/mL, at follow-up (2 weeks of treatment). On an unknown date, Troponin I (0o00-0o04): 0o35 ng/ml (High) 0o35 ng/mL. On an unknown date, White blood cell count (4o0-11o0): 22o1 ×10^9/l (High) 22o1 ×10^9/L, On admission, hospital day 1, 29o9 ×10^9/l (High) 29o9 ×10^9/L, On hospital transfer, hospital day 6, 24o5 ×10^9/l (High) 24o5 ×10^9/L, 3 days after  treatment initiation, hospital day 12 and 21o4 ×10^9/l (High) 21o4 ×10^9/L, at follow-up (2 weeks of treatment).     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter considered STILL'S DISEASE (Adult-onset Still's disease), ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure) and PNEUMONIA (suspected community acquired pneumonia) to be possibly related.    Patient developed a sore throat, intermittent headache, and fever at 5 days after the second dose of the vaccine, approximately one month after the first dose. Over the next few days, she continued to have persistent daily fevers of up to 40°C despite consistent use of acetaminophen and nonsteroidal anti-inflammatory drugs. She subsequently developed severely debilitating myalgias,  arthralgias, and pleurisy that ultimately prompted her to seek medical attention. She was treated empirically with antibiotics for suspected community acquired  pneumonia and her hypoxia resolved within 24 hrs. On the second day of admission she  developed an evanescent salmon-colored rash over the upper back, dorsal aspect of the hands, and bilateral thighs occurring with fevers. Serological testing including rheumatoid factor, cyclic citrullinated peptide antibody IgG, and antinuclear antibody was negative. After a thorough unremarkable infectious and malignancy  work-up was completed, the patient was diagnosed with AOSD. At the time of diagnosis, according to the Yamaguchi classification criteria of AOSD, the patient met three of four major criteria (fever, typical rash, leukocytosis) and four of five minor criteria (sore throat, lymphadenopathy, abnormal liver function tests, and negative rheumatoid factor and antinuclear antibody).The patient started treatment with prednisone 60 mg daily (1 mg/kg per day) with immediate resolution of her fevers and skin rash, and rapid improvement of her arthralgias and myalgias over the subsequent 3 days. There was a worsening thrombocytosis for the first few  days after treatment initiation, which was deemed to be reactive and eventually improved with the rest of the inflammatory markers.  Very limited information regarding the events has been provided at this time.  Further information has been requested.; Sender's Comments: Very limited information regarding the events has been provided at this time.  Further information has been requested.