SUSPECTED IMMUNOLOGICAL VACCINE FAILURE; This spontaneous report was received from literature: Two subsequent doses of mRNA SARS-CoV-2 vaccines in solid organ transplant recipients: A case series. Clinical Transplantation. 2022 Jul 13; 2022/36. This report concerned a 60 year old male of an unspecified race and ethnic origin. The patient's height, and weight were not reported. The patient's past medical history included: kidney transplant (15 years since the transplant). The objective of this article was to study immunogenicity of Ad26.COV2.S Prime and Two Subsequent doses of mRNA SARS-CoV-2 vaccines in solid organ transplant recipients. The patient received covid-19 vaccine ad26.cov2.s (Dose number in series 1) (suspension for injection, route of admin, batch number and expiry were not reported) dose, start therapy date were not reported, 01 total administered for covid-19 prophylaxis. The batch number was not reported and has been requested. Concomitant medications included mycophenolate mofetil (MMF), and tacrolimus for an unspecified indication.  On an unspecified date laboratory test included: Antibody test (anti-RBD) which was less than 0.8 U/mL (Highest Post-D1 (ad26.cov2.s) Titers), 0.97 AU (Highest Post-D2 (elasomeran) Titers), 297 U/mL (Highest Post-D3 (elasomeran) Titers) hence suspected immunological vaccine failure (Dose number in series 1). The reported range of negative sero-response cut-off was anti-RBD less than 0.8 U/mL or anti-S1 less than 1.1 AU. Days between D3 and Post-D3 titers was 31 days. The patient additionally received two doses of non-company suspect vaccine (Spikevax) (mRNA 1273) elasomeran (Dose number in series 2) (form of admin, route of admin, and batch number were not reported, expiry: UNKNOWN) dose was not reported, start therapy date were not reported for covid-19 prophylaxis (Dose number in series 2). The vaccination days in between ad26.cov2.s and elasomeran was 73 days while second dose of elasomeran was after 28 days post first dose of elasomeran. It was unknown whether the patient experienced any adverse events following vaccination with both the doses of elasomeran (Dose number in series 2). The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of suspected immunological vaccine failure was not reported. The authors emphasized on the awareness that despite suboptimal antibody response to the Ad26.COV2.S prime, two subsequent mRNA vaccines increased antibody titers to high levels for the majority of participants, with acceptable side effects. This series suggested that a heterologous vaccine regimen may be a reasonable option for SOTRs (Solid Organ Transplant Recipients) though lack of sero-response, despite two mRNA boosters, suggested that some recipients may remain at risk for SARS-CoV-2 infection. Comparison of the humoral and cellular responses to three-dose heterologous versus homologous vaccination was needed. This report was serious (Other Medically Important Condition). This case, from same Literature article is linked to 20221034754, 20221034707, 20221034752, 20221034742, 20221012832 and 20221034625. This report was associated with product quality complaint.; Sender's Comments: V0: 20221034755-covid-19 vaccine ad26.cov2.s-suspected immunological vaccine failure. The event(s) has an unknown/unclear 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: CONMEDS-OTHER SUSPECT DRUGS, SPECIAL SITUATIONS. Therefore, this event(s) is considered not related.