Initial information received on 19-Jun-2018 regarding an unsolicited valid serious case issued from a literature article. Abstract- Influenza infection and Pneumocystis jirovecii pneumonia (PJP) in hematopoietic stem cell transplant (HSCT) patients are well characterized; however, no dual infections have been reported in this patient population and little evidence of mechanisms of interaction between the two infections exists. We present a 53-year-old male allogeneic HSCT patient on immunosuppressive therapy for the treatment of graft versus host disease initially diagnosed with influenza A H3 and later PJP. Despite the development of acute respiratory distress syndrome, the patient was successfully treated with appropriate antimicrobial therapy and aggressive supportive care. This case demonstrates the necessity of maintaining a high index of suspicion for fungal (including PJP) coinfection or superinfection in the setting of worsening influenza infection. This case involves a 53 years old male patient who experienced influenza a h3, while he received vaccine Influenza vaccine. The patients past medical history included chronic myelomonocytic leukemia type 1 with a high-risk score according to Mayo CMML prognostic model and scoring system. The patient underwent high-dose busulfan and fludarabine followed by matched-unrelated donor allogeneic HSCT around 10 months prior to the presentation. Following transplantation, the patient was maintained on daily mycophenolate mofetil and tacrolimus and a prophylactic regimen that included trimethoprim-sulfamethoxazole (TMP-SMX) and acyclovir. Seven months prior to presentation, his course was complicated by GVHD affecting primarily the gastrointestinal tract, which was treated by high-dose corticosteroids. At that time, the patients PJP prophylaxis was switched to once monthly inhaled pentamidine (300 mg) because of pancytopenia attributed to TMP-SMX therapy. The patients past medical treatment (s), vaccination(s) and family history were not provided. On an unknown date, the patient received a dose of suspect Influenza Vaccine produced by unknown manufacturer lot number not reported via unknown route in unknown administration site. On an unspecified date, the patient was diagnosed with pericardial effusion and bilateral pleural effusions. The pericardial effusion was deemed stable on serial transthoracic echocardiograms, while fluid analysis of the pleural effusions showed transudate. The effusions were attributed to GVHD. Thirteen days prior to the current presentation, the patient complained of shortness of breath and cough as well as a recent sick contact. On examination, he was afebrile, blood pressure was 103/74 mmHg, heart rate was 115 bpm, oxygen saturation at 92 % on room air, respiratory rate of 19/min, in no apparent respiratory distress, and lung sounds clear to auscultation. Computed tomography (CT) of the thorax without contrast exhibited bilateral pleural effusions, pericardial effusion, and very few nonspecific ground glass changes in the upper lobes. Nasal swab was polymerase chain reaction (PCR) positive for influenza A subtype H3. He had a brief admission to the hospital and was discharged on a 10-day course of oseltamivir. Seven days later, the patient presented to the Emergency Department (ED) with complaints of worsening shortness of breath, productive cough, rhinorrhea, congestion, weakness, fever, and chills. At that time, the patient was on corticosteroids equivalent to methylprednisolone 24 mg daily for the management of GVHD. On examination, he was afebrile, blood pressure was 123/94, pulse 122 beats/min, oxygen saturation of 96% on 4 L oxygen via nasal cannula, respiratory rate of 20/min, and rhonchi on lung auscultation. CT thorax revealed large areas of ground glass infiltrates involving the perihila, upper lobes, and middle lobe (Figure 2). A nasal swab was again positive for rapid influenza A PCR. The patient was started on broad-spectrum antibiotics as well as another 10-day course of oseltamivir owing to questionable compliance with the prior oseltamivir therapy. Transthoracic echocardiogram revealed increased pericardial effusion, early diastolic collapse of the right ventricular free wall, and was concerning for impending cardiac tamponade. The day following presentation, the patient underwent a pericardial window procedure, drainage of left pleural effusion as well as lung biopsy, given the presence of ground glass changes on thoracic CT. Postoperatively, the patient was maintained on high-flow oxygen delivered by nasal cannula. The lung biopsy specimen revealed chronic interstitial inflammation, edema, reactive pneumocyte atypia, areas with features of organizing pneumonia, and P. jirovecii. The patient was started on intravenous TMP-SMX and methylprednisolone 35 mg twice daily. Oseltamivir was continued and broad-spectrum antibiotics were discontinued following negative respiratory culture. The patients hypoxia continued to worsen, requiring mechanical ventilation. Bronchoscopy with bronchoalveolar lavage (BAL) during mechanical ventilation revealed both P. jirovecii and influenza A H3 on PCR, with no evidence of other infections. The patient was eventually extubated on day 9 of mechanical ventilation and transferred out of the intensive care unit. He was discharged home on day 27 following admission. He completed a 21-day course of TMP-SMX. Final diagnosis was influenza A Subtype H3. The patient was treated with Oseltamivir and Methylprednisolone. The patient outcome is reported as Not Applicable for vaccination failure, as Unknown for influenza a h3, as Unknown for shortness of breath, worsening shortness of breath, as Unknown for cough, productive cough, as Unknown for rhinorrhea, as Unknown for congestion, as Unknown for weakness, as Unknown for fever, as Unknown for chills and as Unknown for pericardial effusion. Patient was discharged home on day 27 following admission. He completed a 21-day course of TMP-SMX. Sender's Comments: This case concerns an adult patient who presented with influenza, dyspnea, cough, fever, pericardial effusion after vaccination with Influenza vaccine. The time to onset is not known. There is also no information regarding patient's condition at time of vaccination, vaccination schedule and lab tests do not rule out alternate etiologies. Based upon the reported information, the role of the vaccine cannot be assessed.