Pneumonia; This case was reported in a literature article and described the occurrence of pneumonia in a patient who received Flu unspecified (Flu vaccine) for prophylaxis.   Concurrent medical conditions included end stage renal disease (receiving hemodialysis and on the kidney transplant waitlist).   On an unknown date, the patient received Flu vaccine at an unknown dose. On an unknown date, less than 6 months after receiving Flu vaccine, the patient experienced pneumonia (serious criteria hospitalization and GSK medically significant). On an unknown date, the outcome of the pneumonia was unknown.   It was unknown if the reporter considered the pneumonia to be related to Flu vaccine.  Additional details were provided as follows:  This case was reported in a literature article and described the occurrence of pneumonia in a patient of unspecified age and gender who was vaccinated with unspecified influenza (flu) vaccine (manufacturer unknown) for prophylaxis.   The patient was part of a study that aimed to investigate the risk of de novo human leukocyte antigen (HLA) antibody development following flu vaccination in end-stage renal disease (ESRD) patients on the kidney transplant waitlist. The patient had history of ESRD and was receiving hemodialysis. The patient was on waitlist for kidney transplant. [In this study, 31 patients were enrolled, 26 percent were female, mean age was 48 years. At least one antibody was found at baseline in 90% by immunoglobulin M (IgM) and 77% by IgG.]. At baseline, 2 weeks before vaccination, blood sample was drawn and was analyzed by single antigen beads (SAB) for HLA class I and II IgM and IgG antibodies. IgG antibody was present in sample with mean fluorescent intensity (MFI) to DR14 was between 22 and 64, DRB4*01:01 was 23, DP1 was between 39 and 47, DPA1*02:02/DPB1*0.5:0.1 was 12. IgM antibodies was present on sample with MFI to A*02:01 was 130; B8, B46 and B57 all were 0 and DPA1*02:02/DPB1*05:01 was 6. It was reported that antibodies were considered de novo if they had a mean fluorescent intensity (MFI) of less than equal to 250 at baseline. No information on patient's family history or concomitant medication was provided.  On an unspecified date in 2017, the patient received unspecified influenza (flu) vaccine as routine clinical care (administration route and site unspecified, dosage unknown; batch number not provided). The age of vaccination was not provided.   After 10 to 14 days of vaccination, on blood sample analysis, IgG antibody present on sample with MFI to DR14 was between 43 and 94, DRB*01:01 was 78, DP1 was 77 and DPA1*02:02/DPB1*0.5:0.1 was 42. IgM antibodies was present on sample with MFI to A*02:01 was 243, B8 was 232, B46 was 0, B57 was between 1237 and 3505 and DPA1*02:02/DPB1*05:01 was 62. At 6 weeks after vaccination, on blood sample analysis, IgG antibody was present on sample with MFI to DR14 was between 11 and 52, DRB*01:01 was 15, DP1 was between 22 and 23 and DPA1*02:02/DPB1*0.5:0.1 was 0. IgM antibodies was present on sample with MFI to A*02:01 was 150; B8, B46 and B57 all were 0 and DPA1*02:02/DPB1*05:01 was 57.  On an unspecified date, an unknown period post vaccination, the patient was hospitalized with pneumonia. Subsequently, at 6 months post-vaccination, on blood sample analysis, IgG antibody was present on sample with MFI to DR14 was between 561 and 1587, DRB*01:01 was 2576, DP1 was between 3916 and 3970 and DPA1*02:02/DPB1*0.5:0.1 was 7033.  IgM antibodies was present on sample with MFI to A*02:01 was 1155, B8 was 1408, B46 was 1075, B57 was 0 and DPA1*02:02/DPB1*05:01 was 2231. It was reported that antibodies were considered de novo if they had a MFI greater than equal to 1000 at any of the 3 post-vaccine time-points. [In this study, De novo IgM antibody occurred in 15/28 vaccinated and 2/3 unvaccinated pts. De novo IgG antibody occurred in 7/28 vaccinated and 1/3 unvaccinated patients]. De novo antibodies were mostly low strength and IgM specificities somewhat enriched for natural antibodies. De novo IgM-to-IgG isotype switching temporally consistent with flu vaccine response was not observed in the patient.  This case has been considered serious due to hospitalization.  Treatment was unknown.  The outcome of the event was not provided.   The authors did not comment on relationship between the event of pneumonia and unspecified influenza vaccine. The authors stated "De novo IgM-to-IgG isotype switching temporally consistent with flu vaccine response was not observed in any subject. Detection of de novo IgG antibody absent a preceding IgM response is unusual and may represent an antibody recall response following vaccination or other stimulus but is difficult to definitively assign to vaccine."  The authors concluded "Despite small numbers, de novo HLA antibodies occurred in both flu vaccinated and unvaccinated patients (pts). No particular specificity was favored. Detection of de novo IgG antibody absent a preceding IgM response is unusual and may represent an antibody recall response following vaccination or other stimulus but is difficult to definitively assign to vaccine.''      Lab Comments: On an unspecified date Lab test were performed. At baseline 2 weeks before vaccination,  IgG antibody was present in sample with mean fluorescent intensity (MFI) to DR14 was between 22 and 64, DRB4*01:01 was 23, DP1 was between 39 and 47, DPA1*02:02/DPB1*0.5:0.1 was 12. IgM antibodies was present on sample with MFI to A*02:01 was 130; B8, B46 and B57 all were 0 and DPA1*02:02/DPB1*05:01 was 6. It was reported that antibodies were considered de novo if they had a mean fluorescent intensity (MFI) of less than equal to 250 at baseline.After 10 to 14 days of vaccination, on blood sample analysis, IgG antibody present on sample with MFI to DR14 was between 43 and 94, DRB*01:01 was 78, DP1 was 77 and DPA1*02:02/DPB1*0.5:0.1 was 42. IgM antibodies was present on sample with MFI to A*02:01 was 243, B8 was 232, B46 was 0, B57 was between 1237 and 3505 and DPA1*02:02/DPB1*05:01 was 62. At 6 weeks after vaccination, on blood sample analysis, IgG antibody was present on sample with MFI to DR14 was between 11 and 52, DRB*01:01 was 15, DP1 was between 22 and 23 and DPA1*02:02/DPB1*0.5:0.1 was 0. IgM antibodies was present on sample with MFI to A*02:01 was 150; B8, B46 and B57 all were 0 and DPA1*02:02/DPB1*05:01 was 57.at 6 months post-vaccination, on blood sample analysis, IgG antibody was present on sample with MFI to DR14 was between 561 and 1587, DRB*01:01 was 2576, DP1 was between 3916 and 3970 and DPA1*02:02/DPB1*0.5:0.1 was 7033.  IgM antibodies was present on sample with MFI to A*02:01 was 1155, B8 was 1408, B46 was 1075, B57 was 0 and DPA1*02:02/DPB1*05:01 was 2231.