This case was reported in a literature article and described the occurrence of acute respiratory distress syndrome in a adult female patient who received Influenza vaccine Quadrivalent unspecified season. The patient's past medical history included breast cancer (in remission), coronary artery bypass graft, pericarditis (requiring a pericardial window), mediastinitis, hypertension and diabetes mellitus. On an unknown date, the patient received Influenza vaccine Quadrivalent unspecified season at an unknown dose. On an unknown date, an unknown time after receiving Influenza vaccine Quadrivalent unspecified season, the patient experienced acute respiratory distress syndrome (serious criteria death, hospitalization and GSK medically significant), metapneumovirus infection (serious criteria hospitalization and GSK medically significant), pneumothorax (serious criteria death, hospitalization and GSK medically significant), pneumonia (serious criteria hospitalization and GSK medically significant), and shortness of breath (serious criteria hospitalization). On an unknown date, the outcome of the acute respiratory distress syndrome and pneumothorax were fatal and the outcome of the metapneumovirus infection, pneumonia and shortness of breath were unknown. The reported cause of death was acute respiratory distress syndrome and pneumothorax. The reporter considered the acute respiratory distress syndrome, metapneumovirus infection, pneumothorax, pneumonia and shortness of breath to be related to Influenza vaccine Quadrivalent unspecified season. Additional information was provided. This case was reported in a literature article and described the occurrence of human metapneumovirus (MPV) infection in an adult female patient who was vaccinated with unspecified influenza vaccine (manufacturer unknown). The patient was a nursing home resident with history of breast cancer (in remission), coronary artery bypass surgery, pericarditis requiring a pericardial window, mediastinitis, hypertension, and diabetes mellitus. The patient did not report any sick contacts. No information on patient's family history or concomitant medication was provided. On an unspecified date, the patient received unspecified influenza vaccine (administration route and site unspecified; dosages unknown; batch number not provided). On an unspecified date, an unknown period after vaccination, the patient presented with shortness of breath and clinical evidence of pneumonia. The patient's white cell count was elevated with a left shift in differential count (range and normal value not provided). There was confirmatory evidence on chest X-ray in the form of infiltrates. [In this study, 3 out of the 4 patients received a CT scan of the chest confirming extensive bilateral infiltrates and evidence of pulmonary oedema suggesting acute respiratory distress syndrome (ARDS)]. It was reported that the patient had evidence of pneumonia with evidence of respiratory failure, and a rapid respiratory viral panel that confirmed MPV infection. The patient's family refused intubation, and prolonged non-invasive ventilation causing pneumothorax and ARDS results in the patient's demise. It was unknown if the autopsy was performed. This case has been considered serious due to death/hospitalisation. The authors did not comment on the relationship between MPV infection and unspecified influenza vaccine. The authors concluded that "The disease spectrum of MPV can vary widely, and the outcomes vary largely based on comorbidities. The infection can frequently lead to severe respiratory failure, progressing to ARDS and death, in the elderly or debilitated patients." This is 1 of the 2 valid cases in the same literature article.