Multisystem inflammatory syndrome in a fully vaccinated 18-year-old without known SARS-CoV-2 infection; The initial case was missing the following minimum criteria: unspecified product. Upon receipt of follow-up information on (15Sep2022), this case now contains all required information to be considered valid.  This is a literature report.  An 18-year-old female patient received BNT162b2 (BNT162B2), in 2021 as dose 1, single (Batch/Lot number: unknown) and in Apr2021 as dose 2, single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "emergency department" (unspecified if ongoing). The patient's concomitant medications were not reported. The following information was reported: MULTISYSTEM INFLAMMATORY SYNDROME IN ADULTS (hospitalization, medically significant, life threatening) with onset 2021, 6 months after the suspect product(s) administration, outcome "recovered" (2021), described as "Multisystem inflammatory syndrome in a fully vaccinated 18-year-old without known SARS-CoV-2 infection". The patient was hospitalized for multisystem inflammatory syndrome in adults (start date: Oct2021, hospitalization duration: 10 day(s)).  The patient underwent the following laboratory tests and procedures: Alanine aminotransferase (8-24): (unspecified date) 36 IU/l, notes: On hospital day 1; (unspecified date) 53 IU/l, notes: On hospital day 3; (unspecified date) 27 IU/l, notes: On hospital day 5; (unspecified date) 24 IU/l, notes: On hospital day 7; (Oct2021) 44 IU/l, notes: Admission; Aspartate aminotransferase (13-35): (unspecified date) 44 IU/l, notes: On hospital day 1; (unspecified date) 96 IU/l, notes: On hospital day 3; (unspecified date) 52 IU/l, notes: On hospital day 5; (unspecified date) 57 IU/l, notes: On hospital day 7; (Oct2021) 66 IU/l, notes: Admission; Blood albumin (4.0-5.1): (unspecified date) 3.2 g/dl, notes: On hospital day 1; (unspecified date) 2.7 g/dl, notes: On hospital day 3; (unspecified date) 2.8 g/dl, notes: On hospital day 5; (unspecified date) 2.5 g/dl, notes: On hospital day 7; (Oct2021) 4.1 g/dl, notes: Admission; Blood bilirubin (0.1-0.8): (unspecified date) 0.9 mg/dl, notes: On hospital day 1; (unspecified date) 2.1 mg/dl, notes: On hospital day 3; (unspecified date) 2.2 mg/dl, notes: On hospital day 5; (unspecified date) 0.6 mg/dl, notes: On hospital day 7; (Oct2021) 1.3 mg/dl, notes: Admission; Blood creatinine (0.60-0.88): (unspecified date) 0.94 mg/dl, notes: On hospital day 1; (unspecified date) 0.66 mg/dl, notes: On hospital day 3; (unspecified date) 0.8 mg/dl, notes: On hospital day 5; (unspecified date) 0.56 mg/dl, notes: On hospital day 7; (Oct2021) 1.04 mg/dl, notes: Admission; Blood culture: (unspecified date) No growth, notes: On hospital day 1; (unspecified date) Unknown result, notes: On hospital day 3; (unspecified date) Unknown result, notes: On hospital day 5; (unspecified date) Unknown result, notes: On hospital day 7; (Oct2021) Unknown result, notes: Admission; Blood lactic acid (0.5-2.2): (unspecified date) 5.7 mmol/L, notes: On hospital day 1; (unspecified date) 5.5 mmol/L, notes: On hospital day 3; (unspecified date) 3.4 mmol/L, notes: On hospital day 5; (unspecified date) 2.1 mmol/L, notes: Improved.On hospital day 5; (Oct2021) Unknown result, notes: Admission, Elevated; Blood pressure measurement: (unspecified date) 86/53 mmHg, notes: Hypotensive; (unspecified date) 70s/50s, notes: Fluid refractory hypotension. On hospital day 1; Blood sodium (136-145): (unspecified date) 134 mmol/L, notes: On hospital day 1; (unspecified date) 137 mmol/L, notes: On hospital day 3; (unspecified date) 134 mmol/L, notes: On hospital day 5; (unspecified date) 134 mmol/L, notes: On hospital day 7; (Oct2021) 140 mmol/L, notes: Admission; Body temperature: (unspecified date) Febrile, notes: On hospital day 2; (unspecified date) Febrile; (unspecified date) Afebrile, notes: for 24 h by HD 5; Computerised tomogram: (unspecified date) finding of retropharyngeal fluid collection led to, notes: septic shock secondary to a retropharyngeal abscess as the alternative diagnosis; Computerised tomogram neck: (unspecified date) demonstrated moderate decrease in the, notes: retropharyngeal fluid collection. On hospital day 2; (unspecified date) demonstrated a retropharyngeal fluid collection, notes: (6.1x2.7x0.5 cm) extending from C1 to C4; C-reactive protein (0.1-1.7): (unspecified date) 352.4 mg/l, notes: Elevated CRP, On hospital day 1; (unspecified date) 415.0 mg/l, notes: Elevated CRP, On hospital day 3; (unspecified date) 327.5 mg/l, notes: Elevated CRP, On hospital day 5; (unspecified date) 118.6 mg/l, notes: Improved, Elevated CRP,On hospital day 7; (Oct2021) 400.7 mg/l, notes: Elevated CRP, Admission; Culture urine: (unspecified date) No growth, notes: On hospital day 1; (unspecified date) Unknown result, notes: On hospital day 3; (unspecified date) Unknown result, notes: On hospital day 5; (unspecified date) Unknown result, notes: On hospital day 7; (Oct2021) Unknown result, notes: Admission; Echocardiogram: (unspecified date) repeated ECHO demonstrated improvement in, notes: cardiac function with LVEF of 42%, On hospital day 2; (unspecified date) ventricular function improved on ECHO, notes: (LVEF 55%) on HD  4 on vasopressors); (unspecified date) demonstrated normal biventricular function, notes: On hospital day 9; (unspecified date) which showed an LVEF of 59% with no valve, notes: or coronary abnormalities. At her follow up appointment with Cardiology 12 days after discharge; (Oct2021) showed markedly depressed biventricular function, notes: with a left ventricular ejection fraction (LVEF) of 22%; Ejection fraction: (unspecified date) Normal, notes: was obtained three weeks after discharge; Ejection fraction: (unspecified date) 42 %, notes: On hospital day 2; (unspecified date) 55 %, notes: On hospital day 4; (unspecified date) 59 %, notes: at her follow up appointment with Cardiology 12 days after discharge; (Oct2021) 22 %; Haemoglobin (11.8-16.0): (unspecified date) 9.4 mg/dl, notes: On hospital day 1; (unspecified date) 9.5 mg/dl, notes: On hospital day 3; (unspecified date) 8.6 mg/dl, notes: On hospital day 5; (unspecified date) 9.0 mg/dl, notes: On hospital day 7; (Oct2021) 12 mg/dl, notes: Admission; Heart rate: (unspecified date) 127, notes: Units: Beats/per minute tachycardic; Heart rate: (unspecified date) 150 seconds, notes: tachycardic,On hospital day 1; Influenza virus test: (unspecified date) Negative; exam: (unspecified date) she had tender bilateral cervical lymphadenopathy, notes: trismus, fullness on the left side of her neck, and decreased range of neck motion; (unspecified date) no conjunctivitis or rash; Lymphocyte count (1.10-3.50): (unspecified date) 1.50, notes: Units: X10 3 /mcL,On hospital day 1; (unspecified date) 0.57, notes: Units: X10 3 /mcL, On hospital day 3; (unspecified date) 2.58, notes: Units: X10 3 /mcL, On hospital day 5; (unspecified date) 1.03, notes: Units: X10 3 /mcL, On hospital day 7; (Oct2021) 0.48, notes: Units: X10 3 /mcL, Admission; Magnetic resonance imaging heart: (unspecified date) normal EF without evidence of myocardial, notes: inflammation by parametric mapping and there was no late gadolinium enhancement of the myocardium. was obtained three weeks after discharge; Mononucleosis heterophile test: (unspecified date) Negative; Neutrophil count (1.60-8.10): (unspecified date) 17.20, notes: Units: X10 3 /mcL, On hospital day 1; (unspecified date) 20.52, notes: Units: X10 3 /mcL, On hospital day 3; (unspecified date) 17.47, notes: Units: X10 3 /mcL, On hospital day 5 (unspecified date) 22.80, notes: Units: X10 3 /mcL, On hospital day 7(Oct2021) 12.22, notes: Units: X10 3 /mcL, Admission; Platelet count (135-371): (unspecified date) 224, notes: Units: X10 3 /mcL, On hospital day 1; (unspecified date) 234, notes: Units: X10 3 /mcL, On hospital day 3 (unspecified date) 223, notes: Units: X10 3 /mcL, On hospital day 5 unspecified date) 271, notes: Units: X10 3 /mcL, On hospital day 7 (Oct2021) 200, notes: Units: X10 3 /mcL, Admission; Procalcitonin (normal high range 0.24): (unspecified date) Greater than 100.00, notes: On hospital day 1; (unspecified date) Greater than 100.00, notes: On hospital day 3; (unspecified date) Unknown result, notes: On hospital day 5; (unspecified date) Unknown result, notes: On hospital day 7; (Oct2021) Elevated, notes: Admission; Protein total: (unspecified date) Positive, notes: On hospital day 6; Pulmonary function test: (unspecified date) Normal; SARS-CoV-2 antibody test: (unspecified date) Unknown result, notes: On hospital day 1; (unspecified date) Positive, notes: On hospital day 3; (unspecified date) Unknown result, notes: On hospital day 5; (unspecified date) Unknown result, notes: On hospital day 7; (unspecified date) Positive, notes: On hospital day 6 (drawn prior to IVIG treatment); (Oct2021) Unknown result, notes: Admission; SARS-CoV-2 test: (unspecified date) Negative, notes: weekly for 2  months prior to presentation as part of routine screening at her college. She had no known symptomatic SARS-CoV-2 infection; (unspecified date) Negative; (unspecified date) Negative; Streptococcus test: (unspecified date) Negative; Troponin I (normal high range 0.03): (unspecified date) Unknown result, notes: On hospital day 1; (unspecified date) 0.22 ng/ml, notes: On hospital day 3; (unspecified date) 0.18 ng/ml, notes: On hospital day 5; (unspecified date) Unknown result, notes: On hospital day 7; (Oct2021) Elevated, notes: Admission; White blood cell count (3.9-10.7): (unspecified date) 19.0, notes: Units: X10 3 /mcL persistent leukocytosis on hospital day 1 significant for leukocytosis; (unspecified date) 22.8, notes: Units: X10 3 /mcL persistent leukocytosis, On hospital day 3 significant for leukocytosis; (unspecified date) 221., notes: Units: X10 3 /mcL persistent leukocytosis, On hospital day 5 significant for leukocytosis; (unspecified date) 29.3, notes: Units: X10 3 /mcL, persistent leukocytosis On hospital day 7 significant for leukocytosis; (Oct2021) 13.8, notes: Units: X10 3 /mcL persistent leukocytosis, Admission significant for leukocytosis.  Case presentation: A previously healthy 18-year-old (withheld) female presented to the emergency department (ED) with four days of fever, fatigue, headache, sore throat, odynophagia, abdominal pain, vomiting, and diarrhea. Prior to presentation to the ED, she had tested negative for Group A Streptococcus, influenza, mononucleosis, and SARS-CoV-2. She completed her Pfizer-BioNTech mRNA COVID-19 two-dose vaccine series six months ago, and had tested negative (rapid antigen) weekly for 2 months prior to presentation as part of routine screening at her college. She had no known symptomatic SA RS- COV-2 infection. In the ED, she was afebrile, tachycardic at 127 beats per minute and hypotensive with a blood pressure of 86/53 mmHg. On exam, she had tender bilateral cervical lymphadenopathy, trismus, fullness on the left side of her neck, and decreased range of neck motion. Pertinent negatives included no conjunctivitis or rash, and normal lung exam. Her initial workup was significant for leukocytosis, elevated CRP, and negative SARS-CoV-2 PCR. Neck commuted tomography (CT) scan demonstrated a retropharyngeal fluid collection (6.1 x 2.7 x 0.5 cm) exempting from CI to CA. A diagnosis of retropharyngeal phlegmon was made and IV ampicillin-sulbactam was started in addition to a single dose of dexamethasone for airway edema. CT of the neck demonstrating a retropharyngeal fluid collection presumed to be the source for the patient's original presentation. Arrows indicate sagittal view of retropharyngeal fluid collection measuring 6.1 cm, from CI to C4 (left) and a coronal view of retropharyngeal fluid collection measuring 2.7 x 0.5 cm (right). On the day after admission [Hospital Day (HD) Il, she was tachycardic to the [30s, hypoxemic requiring supplemental oxygen by nasal cannula, and development fluid refractory hypotension with blood pressures of 70s/50s mmHg. She was transferred to the pediatric intensive care unit (PICU) and started on norepinephrine for presumed septic shock. Labs were notable for elevated procalcitonin, lactate and troponin, in addition to persistent leukocytosis. Antibiotics were broadened from ampicillin-sulbactam to vancomycin, clindamycin, and levofloxacin. Echocardiogram (ECHO) showed markedly depressed biventricular function with a left ventricular ejection fraction (LVEF) of 22%. Norepinephrine was transitioned to epinephrine for inotropic support and dobutamine was added. Respiratory support was escalated to high flow nasal cannula and briefly to bilevel positive airway pressure due to hypoxemia and increased work of breathing. On HD 2, she remained febrile, tachycardic, and tachypneic despite a repeat neck CT that demonstrated moderate decrease in the retropharyngeal fluid collection. Repeat ECHO demonstrated improvement in cardiac function with LVEF of 42% while on vasopressors. On HD 3, her antibiotics were broadened to vancomycin, cefepime and metronidazole to cover for indolent infection given her lack of clinical improvement and persistently elevated CRP to 415 mg/L. Given her continued critical illness on multiple vasopressors and broad-spectrum antibiotics, MIS-C was considered in the differential diagnosis, and the decision was made to administer intravenous immune globulin (IVIG). She received IVIG on HD 3 and received a total of 2 g/kg of IVIG; given her heart failure and initial LVEF, it was administered over the course of four days (HD 3-HD 6). After initiation of IVIG, she began to defervesce (afebrile for 24 h by HD 3), and her CRP and lactate improved. Her ventricular function improved on ECHO (LVEF 53% on HD 4 on vasopressors). On HD 6, her COVID-19 IgG (drawn prior to IV IG treatment) to nucleocapsid protein returned positive, and the diagnosis of MIS-C was made. Anti-inflammatory treatment for MIS-C was initiated with intravenous methylprednisolone and subcutaneous anakinra. On HD 7, she was weaned from vasopressor support and transferred back to the to the acute care floor where she continued to recover. ECHO on HD 9 demonstrated normal biventricular function. She was discharged home on HD 10 with subcutaneous anakinra and continued steroids. A timeline demonstrating key events in the chronology of the patient's presentation and subsequent interventions. PICU-pediatric intensive care unit; IVIG, intravenous immunoglobulin; MIS-C, multisystemic inflammatory syndrome in children. She had an ECHO at her follow up appointment with Cardiology 12 days after discharge which showed an LVEF of 59% with no valve or coronary abnormalities. She completed anakinra and prednisone tapers per instructions by Pediatric Rheumatology. Cardiac magnetic resonance imaging (MRI) was obtained three weeks after discharge with normal EF without evidence of myocardial inflammation by parametric mapping and there was no late gadolinium enhancement of the myocardium. Per patient report she has made full recovery with no sequelae.  Discussion and conclusion: The CDC issued a Health Advisory on May 14, 2020, that defined a febrile syndrome following SARS-CoV-2 infection as MIS-C and provided case criteria. It includes a positive test for current or recent SARS-CoV-2 infection or exposure to a suspected or confirmed CO VID- 19 case within the 4 weeks prior to the onset of symptoms, in addition to clinical syndrome and laboratory findings, and no alternative plausible diagnoses. Here the authors reported a case of MIS-C in a teenage female who was fully immunized six months prior to presentation, had tested negative weekly at her college for the two months prior to presentation, and had no known COVID- 19 exposure or symptomatic infection. There have been few reports of MIS-C in fully vaccinated children as of December 2021, one child with sickle cell disease and one with no significant medical history reported. An early release of a CDC report in January 2022 identified five fully vaccinated children who developed MIS-C between July and December 2021, estimating vaccine effectiveness against MIS-C. Only one of the aforementioned cases required vasoactive, and this patient was in both severe cardiogenic shock and hypoxemic respiratory failure. This patient presented with signs and symptoms, as well as laboratory and radiographic findings of MIS-C; however, her vaccination status and negative surveillance tests reduced the pre-test probability. Her CT scan finding of retropharyngeal fluid collection led to septic shock secondary to a retropharyngeal abscess as the alternative diagnosis, and she was treated accordingly. Cases of MIS-C with retropharyngeal edema and/or phlegmon have been reported, though they are neither common nor defining features of MIS-C. The authors weighed the risks and benefits of MIS-C treatments, and decided to trial I VIG but hold methylprednisolone for concerns of serious bacterial infections until the confirmation of her past COVID- 19 infection. Antibodies against SARS-CoV-2 viral spike proteins are elicited by vaccines and confer immunity, whereas COVID- 19 antibody tests that detect nucleocapsid proteins of the SARS-CoV-2 virus indicate natural infection. Her COVID-19 IgG to nucleocapsid protein later returned positive, meeting the missing criterium of positive serology and confirming the diagnosis of MIS-C. Once she was started on treatment for MIS-C, she progressed to full recovery. MIS-C is well described and defined, but the role for COVID- 19 vaccines in preventing MIS-C is assumed but not clearly established. Her vaccination did not cause her MIS-C as she was far out from her vaccination, and she tested positive for COVID-19 IgG antibody to nucleocapsid protein. The patient likely had a breakthrough infection that went undetected. Her case is unique in the degree of shock she presented with secondary to her MIS-C despite of vaccination. Her delay in diagnosis led to unnecessary antibiotic exposure, prolongation of her ICU length of stay, and put her at increased risk for ICU delirium. Given the recent Omicron waves and the ongoing evolution of a dynamic international pandemic with evolving variants, providers should have clinical suspicion for MIS-C when clinical signs and symptoms are consistent with the diagnosis, even in a previously healthy, fully vaccinated child. It is worth consideration that her cardiac MRI performed following her discharge showed near normal function and no residual inflammation. Further investigation into whether vaccination provides additional prevention against long-term sequelae from MIS-C is warranted. Given the broad range of providers (general practitioner, emergency medicine, hospitalist medicine, and critical care) that are involved in the care of these children, her presentation, and patients similar to her are critical for the field to be aware of.; Sender's Comments:  Based on the current available information and the plausible drug-event temporal association, a possible contributory role of the suspect product BNT162B2 to the development of the reported event MULTISYSTEM INFLAMMATORY SYNDROME IN ADULTS Cannot be excluded.  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.