CONFIRMED CLINICAL VACCINATION FAILURE; CONFIRMED COVID-19 INFECTION; REVACCINATION WITH DIFFERENT COVID-19 VACCINE; This spontaneous report received from a patient via other company (Pfizer) concerned a patient of an unspecified age, sex, race and ethnicity. Initial information was processed along with the additional information received on 21-MAR-2023.  The patient's height, and weight were not reported. The patient's concurrent conditions included: drug allergy (unspecified). The patient initially received covid-19 vaccine ad26.cov2.s (dose number in series 1) (suspension for injection, route of admin not reported, batch number: unknown, expiry: unknown) 1 in total, dose and start therapy date were not reported for covid-19 prophylaxis. The batch number was not reported. The Company is unable to perform follow-up to request batch/lot numbers. Concomitant medications included sertraline. The patient additionally received Non-company suspect vaccine included: Pfizer BioNTech Covid-19 vaccine (tozinameran) (Dose number in series 2) ( form of admin, route of admin, and batch number were not reported) dose and start therapy date were not reported, administered to left arm for covid-19 prophylaxis. The patient additionally received Non-company suspect vaccine included: Pfizer BioNTech Covid-19 vaccine (tozinameran) (Dose number in series 3) ( form of admin, route of admin, and batch number were not reported) dose was not reported, administered on 14-OCT-2022 to left arm for covid-19 prophylaxis which was associated with revaccination with different covid-19 vaccine (Dose number in series 3).  On an unspecified date in 2023, the patient experienced covid-19 and was isolated for weeks to pass incubation period for which the patient was given non-company suspect drug Paxlovid, (nirmatrelvir/ritonavir) (form of admin, route of admin, batch number and expiry date were not reported) dose and frequency were not reported from 16-FEB-2023 to 22-FEB-2023 for treatment of covid-19.  On 01-MAR-2023, 7 days after completion of Paxlovid treatment, the patient tested negative for covid-19 virus test. On 08-MAR-2023, 14 days after Paxlovid treatment, the patient started sneezing and experienced head cold returned. The patient tested for covid-19 virus test on 08-MAR-2023 and was positive again which was confirmed covid-19 infection (dose number in series 3) which resulted confirmed clinical vaccination failure (dose number in series 1). The action taken with covid-19 vaccine ad26.cov2.s, tozinameran (Dose number in series 2), and tozinameran (Dose number in series 3) was not applicable; and action taken with nirmatrelvir/ritonavir was not reported. The patient was recovering from confirmed covid-19 infection, and the outcome of confirmed clinical vaccination failure and revaccination with different covid-19 vaccine was not reported. This report was serious (Other Medically Important Condition). This report was associated with a product quality complaint: 90000275764.; Sender's Comments: V0- 20230349681- confirmed clinical vaccination 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.