CONFIRMED CLINICAL VACCINATION FAILURE; CONFIRMED COVID-19 INFECTION; REVACCINATION WITH DIFFERENT COVID-19 VACCINE; This spontaneous report was received from literature. This report concerned a 40 year old female. Initial information was processed along with additional information on 11-OCT-2022. 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's height, and weight were not reported. The patient's past medical history included: liver transplant (0.4 years since transplant surgery), and other pre-existing medical conditions included: The patient was immunocompromised. The patient did not had covid-19 prior to vaccine. The patient received covid-19 vaccine ad26.cov2.s (Dose number in series 1) (suspension for injection, route of admin, and batch number were not reported, expiry: UNKNOWN) dose was not reported, 1 total, start therapy date was not reported for covid-19 prophylaxis. The duration between dose 1 and dose 2 was 75 days. The batch number was not reported. Per procedure, no follow-up will be requested for this case. Concomitant medications included mycophenolate mofetil, tacrolimus and steroids as a triple immunosuppression therapy during the peri- vaccination period.  The patient 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 which was revaccination with different covid-19 vaccine (Dose number in series 2). The duration between dose 2 and dose 3 was 166 days. Days between D3 and post-D3 titers was 76 days. On an unspecified date, the patient experienced confirmed covid-19 infection 47 days after third dose of mRNA-1273 (symptoms included 7 days of mild cough and pharyngitis, during which the monoclonal antibody bamlanivimab/etesevimab was administered (on day 2). No oral antiviral medications were used) (Dose number in series 2) and had confirmed clinical vaccination failure (Dose number in series 1). Laboratory data (dates unspecified) included: Home test-confirmed breakthrough SARS-CoV-2 infection. It was reported that, the highest antibody results collected after doses 2 (D2) and 3 (D3) on the Roche Elecsys Anti-SARS-CoV-2 enzyme immunoassay (EIA) (antireceptor binding domain [RBD], negative less than 0.8 U/ml) or (E) EUROIMMUN EIA (anti-S1, negative less than 1.1 AU) were compared. High-positive (anti-RBD more than or equal to 250 U/ml or anti-S1 more than or equal to 4 AU) levels were defined according to reported association with neutralization of wild-type virus. The anti-RBD was 6.5 U/mL 20 days post-second dose. No pre-infection sample was collected after third dose, but their anti-RBD (anti-receptor binding domain) was greater than 2500 U/mL 29 days post-breakthrough and less than 0.8 R (Highest post-D1 titers) (R: Roche anti-RBD EIA (units: U/ml).  The action taken with covid-19 vaccine ad26.cov2.s, and elasomeran was not applicable. The outcome of the confirmed covid-19 infection, confirmed clinical vaccination failure and revaccination with different covid-19 vaccine 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.  This report was serious (Other Medically Important Condition). This report was associated with product quality complaint: 90000254885.; Sender's Comments: V0: 20221012832-covid-19 vaccine ad26.cov2.s- confirmed clinical vaccination failure. 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. Therefore, this event(s) is considered not related.  20221012832-covid-19 vaccine ad26.cov2.s- confirmed covid 19 infection. 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: MEDICAL HISTORY ( Patient' s history of liver transplant, preexisting immunocompromised state is considered as confounding factors) . Therefore, this event(s) is considered not related