SUSPECTED IMMUNOLOGICAL VACCINE FAILURE; This spontaneous report was received from health professional via literature. This report concerned multiple (unspecified numbers) patients. The objective of the authors was to evaluated SARS-CoV-2 spike-binding IgG antibody levels following COVID-19 vaccination among non-Hodgkin lymphoma and multiple myeloma CAR T therapy recipients. Author's evaluated 104 patients that received CAR T therapy; of those 17 patients (13 patient) were evaluated for antibody spike titers following CAR T therapy. They found that only a minority of non-Hodgkin lymphoma and multiple myeloma patients were able to mount a clinically relevant (greater than 250 IU/mL) antibody response. Testing was performed using the Roche Elecsys anti-SARS-CoV-2 reagent assay. Antibody levels greater than 0.8 U/mL were considered positive per author's laboratory guidelines. Six patients received the mRNA-1273 vaccine, 6 received the BNT162b2 vaccine, 2 received the Ad26.COV2.S vaccine, and 2 were unknown. The patient's height, and weight were not reported. The patient's past medical history included: covid-19 (2), and concurrent conditions included: non-hodgkin lymphoma (10 NHL), and multiple myeloma (7 MM). The patients received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin, batch number and expiry date were not reported) dose, start therapy date were not reported, 1 total administered for covid-19 prophylaxis. The batch number was not reported. Per procedure, no follow-up will be requested for this case. Patients were received IVIG (Intravenous immune globulin), and CAR T (chimeric antigen receptor T-cells) infusions for there concurrent conditions. On an unspecified date, the patients experienced suspected immunological vaccine failure. Laboratory data (dates unspecified) included: COVID-19 antibody test 13 patient were positive, 4 patients were negative and seventy seven percents (n equal to 13) had vaccine immunogenicity according to author's initial antibody spike values greater than 0.8 U/mL. Using a positivity cutoff of 50 IU/mL (at least partial response), vaccination immunogenicity in samples was 47 percent (n equal to 8). Using a positivity cutoff of 250 IU/mL (clinically relevant response), vaccination immunogenicity in samples was 29 percent (n equal to 5). The median time from vaccination to antibody testing was 95 days (6- 792) ; Immunoglobulin G median 553 g/L (range Less than 300-3611), Median range for Reticulocyte count (NR: 0.28 - 3.43) 0.73 10*4/uL, T-lymphocyte count (NR: 34 - 543) 137 10*4/uL, and White blood cell count (NR: 1.3 - 28.2) 5 10*4/uL, Body mass index median 28 (range 18.3 -34.7). The authors concluded that the frequency of vaccination immunogenicity in patients who underwent CAR T therapy among patients with NHL and MM was dependent on positivity cutoff values. Indeed, many studies use differing assays and cutoff values to define seroconversion rates. Approximately one-third of patients that had evaluable antibody spike values following COVID-19 vaccination and CAR T therapy were able to mount an immune response using the strictest criteria for vaccination immunogenicity in relatively small sample. These findings emphasize that cutoff values need to be better defined. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of suspected immunological vaccine failure was not reported. This report was serious (Other Medically Important Condition).; Sender's Comments: V0-20230417738- Suspected immunological vaccine failure-The event has a unknown/unclear temporal relationship, is unlabeled, and has unknown scientific plausibility. There are other factors more likely to be associated with the event. Specifically: SPECIAL SITUATIONS. Therefore, this event is considered inconsistent with vaccine administration.