left glenohumeral joint septic arthritis and left shoulder septic bursitis; left glenohumeral joint septic arthritis and left shoulder septic bursitis; diagnosis of expected postvaccination pain; This is a literature report   The patient is a 68-year-old right-hand dominant woman (59 kg) with a medical history of hypertension, hyperlipidemia, and diverticulitis presented to the emergency department complaining of dull left shoulder pain and decreased range of motion after receiving the COVID-19 Pfizer-BioNTech vaccine (Lot: EL1284) 3 days before presentation. The vaccine was administered using either a VanishPoint 1 mL syringe with a retractable hypodermic 25 gauge (G) 1-inch needle or a BD Eclipse 25 G 1-inch needle. Before injection, a sterile alcohol preparation pad was used to wipe the overlying deltoid injection site. The patient was discharged with unremarkable history and physical examination and diagnosis of expected post vaccination pain. The patient returned to the emergency department 4 days later with severe progressive left shoulder pain and decreased range of motion. Vital signs on presentation included oral temperature of 37.3 degree C (99.2 degree F) with subjective chills. The patient reported no history of trauma to the area and no respiratory or urinary symptoms concerning for infection. On physical examination, she was in no acute distress. Examination of her left shoulder revealed no skin abnormalities, moderate edema, and warmth present at the anterolateral deltoid. Passive range of motion of the left shoulder was limited to 30 degree flexion, 40 degree abduction, 10 degree external rotation, and 40 degree internal rotation with significant limitation in range of motion due to pain. Active range of motion was also severely limited secondary to pain. Neurovascular examination was unremarkable. Laboratory studies demonstrated white blood cell (WBC) count of 9,100 cells/uL (4,500-10,500 cells/uL), erythrocyte sedimentation rate of 60 mm/hr (0-20 mm/hr), and C-reactive protein of 24.2 mg/dL (0-0.5 mg/dL). Radio graphs of the left shoulder demonstrated no osseous abnormality. Ultrasound was not available at the time of presentation. Magnetic resonance imaging (MRI) of the left shoulder with and without contrast was performed and demonstrated severe subacromial/subdeltoid bursitis, with distention of the subdeltoid component with a large amount of fluid, and a full-thickness rotator cuff tear through the midportion of the supraspinatus. There were marked thickening and enhancement of the synovium, indicative of septic bursitis and arthritis. No intramuscular abscess was observed. A glenohumeral joint aspiration was performed. Cloudy synovial fluid was aspirated with cell count significant for 130,000 WBCs/uL, 95% neutrophils, and fluid glucose 61 mg/dL (blood glucose 92 mg/dL). Gram stain and culture were obtained; however, the results were not available at this time. The history, physical examination, and laboratory studies were consistent with the diagnosis of left glenohumeral joint septic arthritis and left shoulder septic bursitis. The patient underwent left shoulder irrigation and debridement under general anesthesia through a deltopectoral approach. The anterior aspect of the left shoulder was noted to have significant edema without erythema. The subacromial bursa was inflamed and enlarged. On incision through the bursal tissue, significant necrotic debris, expressible purulence, and seropurulent fluid were released. The bursal tissue was significantly inflamed and excised. The necrotic debris was sent for culture. All areas of soft-tissue collection appreciated on MRI had been evaluated and evacuated of infectious fluid. The joint capsule was incised, and cloudy synovial fluid was evacuated from the glenohumeral joint. After irrigation and debridement of the glenohumeral joint, the surgical wound was closed in layers. The patient remained admitted postoperatively and started on intravenous (IV) vancomycin and ceftriaxone until cultures returned. Positive cultures included preoperative synovial aspiration growing Streptococcus viridans, intraoperative glenohumeral joint swab growing Streptococcus gordonii, and a second swab growing Mycelia sterilia. Negative cultures included 2 preoperative blood cultures, 3 intraoperative fungus cultures, 2 bursa/synovial swabs, and 1 bursa/synovial specimen. Per infectious disease recommendations, the patient remained on IV ceftriaxone for 1 week and converted to oral antibiotics for 3 weeks on discharge.  The plain AP radiograph of the left shoulder demonstrated no osseous abnormality of the left shoulder. Coronal fat-suppressed proton density-weighted MRI demonstrated severe subacromial/subdeltoid bursitis, with distention of the subdeltoid component with a large amount of fluid and a full thickness rotator cuff tear through the midportion of the supraspinatus. Axial contrast-enhanced fat-suppressed T1-weighted images showed marked thickening and enhancement of the synovium, indicative of septic bursitis and arthritis.  No follow-up attempts are needed. No further information is expected.; Sender's Comments: Based on the plausible temporal relation, the association between the events of septic arthritis and septic bursitis and the suspect product of BNT162B2 cannot be completely ruled out.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.