ill with respiratory cold; Gave a dose of close to 0.5 ml of undiluted maroon cap vaccine to a 3 year old female patient; Gave a dose of close to 0.5 ml of undiluted maroon cap vaccine to a 3 year old female patient; First dose of Covid19 vaccine monovalent: 14Apr2023; This was patient's second dose of Covid19 vaccine: 30May2023; This is a spontaneous report received from contactable reporter(s) (Nurse and Physician) from medical information team, Program ID: (004756).  A 3-year-old female patient received BNT162b2, BNT162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), on 30May2023 as dose 2 (maroon cap), 0.5 ml single (Lot number: 6K1667, Expiration Date: 20Jun2023) at the age of 3 years intramuscular, in left thigh for covid-19 immunisation. The patient had no relevant medical history. There were no concomitant medications. Vaccination history included: BNT162b2 (DOSE 1, SINGLE, Time: Unknown, LOT: FT9142, EXP: 31Aug2023, Route of administration: Intramuscular, Anatomical location: Left thigh), administration date: 14Apr2023, when the patient was 3-year-old, for COVID-19 immunization. The following information was reported: INAPPROPRIATE SCHEDULE OF PRODUCT ADMINISTRATION (non-serious) with onset 30May2023, outcome "unknown", described as "First dose of Covid19 vaccine monovalent: 14Apr2023; This was patient's second dose of Covid19 vaccine: 30May2023"; PRODUCT PREPARATION ERROR (non-serious), OVERDOSE (non-serious) all with onset 30May2023, outcome "unknown" and all described as "Gave a dose of close to 0.5 ml of undiluted maroon cap vaccine to a 3 year old female patient"; NASOPHARYNGITIS (non-serious) with onset 16Jun2023, outcome "unknown", described as "ill with respiratory cold". Relevant laboratory tests and procedures are available in the appropriate section.  Additional information: As per agent, caller was a Registered nurse. Inquiry clarified. Caller stated she made a mistake with the bivalent vaccine. She didn't realize it was a multi-dose vial; she didnt know they had a multi-dose vial so she gave whole vial without diluting product. Confirmed it was a full multi-dose vial and she gave a dose of close to 0.5 ml of undiluted maroon cap vaccine to a 3 year old female patient. Confirmed date of administration was 30May2023 however the error was just discovered today 12June2023. Patient was not the reporter. Outcome of event was unknown because caller hadn't heard anything from patient. Caller was not aware of treatment. Patient did not had prior Vaccinations within 4 weeks. Adverse events did not require Emergency Room, Physician Office and Intensive Care Unit visit. As of 17Jul2023: It was disconnect in12Jun2023 that was given an entire vial of the 6 month 9 year bivalent COVID vaccine. Dr. withheld was notified and he recommended reaching to Pfizer and the CDC. Pfizer contacted but could not give any recommendations. Pfizer did state that during monovalent trials of 10 mcg that the patient may have an increase in side effects. such as fever, discomfort at injection site and fatigue. on 14Jun2023 mother was contracted about overdose. Dr. withheld also ordered additional lab testingan ECHO and an ECG. Medication error details: Overdose of bivalent COVID vaccine given. The medication error occurred when the product was administered to / taken by the patient. The error was not noticed and intercepted before the product was supplied to the patient. The factor considered to be responsible for the medication error was misunderstanding of instructions by the individual administering the medication. Vaccine facility type was doctor's office/urgent Care. Vaccine was not administered at facility. Prior vaccination and specific relevant test for thromboembolic events with thrombocytopenia was none. The patient did not provide information regarding the reported adverse events with the use of the product. The patient did not experience any adverse event(s) as a consequence of the error. The reporter did not  consider the Pfizer product had a causal effect to the adverse events.  Follow-up attempts are completed. No further information is expected.  Follow-up (17Jul2023): This is a spontaneous follow-up report received from a contactable Physician and Nurse. This Physician and Nurse reported in response to HCP letter sent via follow-up letter which included that: Updated information includes: At Risk classification removed. Reporter details added. Lab data height, weight, Echo. ECG, CBC, CRP, ESR, Troponin, INR and D-Dimer added. Age at vaccination added for historical vaccine, anatomical location updated for historical vaccine. New event Cold added and additional information added.