SUSPECTED IMMUNOLOGICAL VACCINE FAILURE; This solicited literature report received from a health care professional via non-company sponsored study. This report concerned multiple patients (unspecified number) of unspecified age, sex, race and ethnic origin. The purpose of this study was to evaluate the immune response to SARS-CoV-2 vaccine in patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. The patients weight, height, and medical history were not reported. The patients concurrent conditions included: chronic lymphocytic leukemia, and small lymphocytic lymphoma, and other pre-existing medical conditions included: The patients had no known history of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. The patients initiated treatment with 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 and has been requested. No concomitant medications were reported.  This study consisted of 210 patients in the initial cohort, patients had enrolled in this cohort within 4 months of receiving their initial vaccination. Time between vaccination and first serologic assessment was median 59 days (range 8-124 days). The patients underwent serologic assessment at enrollment and at 6 and 12 months.  It was reported that, 33 patients had no evidence of serologic response to the primary vaccination series. 11 patients with negative neutralization assay results of which 9 patients had negative serologic assessments (anti-S) results. On unspecified date, patients underwent laboratory tests (Serologic assessment, Neutralizing antibodies test) with negative or no response, which leads suspected immunological vaccine failure. In this study, serologic response was assessed in all via the Roche Elecsys Anti-SARS-CoV-2 S anti-Spike (anti-S) immunoglobulin G (IgG) assay. Laboratory data (dates unspecified) included: Neutralizing antibodies Negative, reference interval for a negative result was neutralizing dilution 50 (ND50) less than 20, and SARS-CoV-2 antibody test Negative (no evidence of serologic response, the reference range for negative results was less than 0.8 AU/mL. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of suspected immunological vaccine failure was not reported. The reporter provided no causality assessment. Company causality between covid-19 vaccine ad26.cov2.s, and suspected immunological vaccine failure was not related.  The author concluded that importance of attaining some degree of vaccine-mediated immunity as well as the importance of ongoing mitigation strategies and therapeutics. This report was serious (Other Medically Important Condition).; Sender's Comments: V0: 20230942559-suspected immunological vaccine failure. The event has a compatible/suggestive 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.