DECREASED ANTIBODY RESPONSES TO AD26.COV2.S; This spontaneous report was received from literature report. Decreased Antibody Responses to Ad26.COV2.S Relative to SARS-CoV-2 mRNA Vaccines in Patients with Inflammatory Bowel Disease. Gastroenterology. This report concerned multiple patients. Initial information was processed along with the additional information received on 24-AUG-2021. The patients' height, and weight were not reported. The patients' concurrent condition included: inflammatory bowel disease. The patients received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin, and batch number were not reported) dose, start therapy date were not reported 1 total for prophylactic vaccination. The batch number was not reported and has been requested. No concomitant medications were reported.  Currently, three vaccines have been granted emergency use authorization for coronavirus disease 2019 (COVID-19) prevention. These include the mRNA platform vaccines (mRNA-1273 (Moderna/NIH) and BNT162b2 (Pfizer-BioNTech)) and an adenovirus vector vaccine (Ad26.CoV2.S (J&J)), which were 94%, 95%, and 67% effective against COVID19 infection in their Phase III registry trials against the endemic variants at the time, respectively. The Patients with inflammatory bowel disease (IBD) on corticosteroids, immunomodulators and advanced therapies may have normal to slightly decreased humoral responses to the SARS-CoV-2 mRNA vaccine platforms and patients receiving infliximab and/or thiopurines have significantly lower rates of seroconversion than those on vedolizumab monotherapy following a single dose of either BNT162b2 or ChAdOx.  Among 353 vaccine recipients with IBD participating in a prospective SARS-CoV-2 vaccine registry without prior COVID-19 infection who had completed a full vaccine regimen, 148 (42%), 193 (55%), and 12 (3%) received mRNA-1273, BNT162b2 and Ad26.CoV2.S respectively. Demographic and disease characteristics were similar across vaccine groups. Approximately 290 (83.1%) of participants were on immune-modifying therapies (IMT) as defined by receipt of advanced therapies (biologics or Janus kinase (JAK)-inhibitors, 80.2%), immunomodulators (16.6%), and/or systemic corticosteroids (6.6%) at the time of initial vaccination. Upon completion of vaccine regimen, whole blood was collected from local patients by venipuncture at three different time points, after regimen completion (2-13 days after completing regimen), week 2 (14-29 days after completing regimen), and week 8 (42-84 days after completing regimen). For participants unable to provide in-person samples, whole blood was collected using the TASSO-SST device at week 8 only (42-84 days after completing regimen). The plasma antibodies to the viral spike protein receptor binding domain [IgG(S-RBD)] were analysed using the SARS-CoV-2 IgG-II assay at each time point, IgG(S)=50 AU/mL was defined as a positive response.  Two weeks after completion of the vaccine regimen, positive antibody levels was detected in 121 (100%), 142 (99%), and 9 (90%) patients receiving mRNA-1273, BNT162b2 and Ad26.CoV2.S, respectively. Quantitative log10 (anti-Spike IgG) levels at both two weeks (14  29 days after regimen completion) and eight weeks (42  84 days after regimen completion) were significantly higher among recipients of mRNA-1273 and BNT162b2 compared with Ad26.CoV2.S (two weeks: 4.20 vs 3.92 vs 1.96 for mRNA-1273, BNT162b2 and Ad26CoV2.S, respectively; at least eight weeks: 3.72 vs 3.41 vs 2.65, respectively). Positive levels of IgG(S) was achieved in all IBD vaccine recipients regardless of vaccine type and IMT use. However, it was found that recipients of Ad26.CoV2.S had significantly lower antibody levels than recipients of mRNA platform vaccines, independent of IMT use.  Conclusion: The clinical implications of qualitatively positive but quantitatively lower antibody levels among Ad26.CoV2.S recipients were unknown. It was not known whether lower antibody titers increase susceptibility to SARS-CoV-2 clinical infection; correlations between immune responses and protection from COVID-19 hospitalization and death are needed. Although the clinical implications of positive but low titers were unclear, further comparative effectiveness research of humoral, cellular, and clinical immunity across SARS-CoV2 vaccine platforms was urgently needed to clarify optimal booster vaccine strategies, particularly among immunocompromised patients. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of decreased antibody responses to ad26.cov2.s was not reported. This report was serious (Other Medically Important Condition). The case is associated with Product Quality Complaint number: 90000190820 This case, from the same reporter is linked to 20210514981, 20171211088, 20171206472, 20180416031 and 20121202239.; Sender's Comments: V0- 20210834287covid-19 vaccine ad26.cov2.s-Decreased antibody responses to ad26.cov2.s-. This event(s) is considered not related. The event(s) 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(s) than the drug. Specifically: SPECIAL SITUATIONS