No adverse event; Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.; Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.; This spontaneous case was reported by an other health care professional and describes the occurrence of COVID-19 IMMUNISATION (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.), INTERCHANGE OF VACCINE PRODUCTS (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.) and NO ADVERSE EVENT (No adverse event) in a 2-year-old female patient who received mRNA-1273.815 (SPIKEVAX 2023-2024) (batch no. AU5509B) for COVID-19 prophylaxis.     Reporter did not report any medical history or condition.  Previously administered products included for Product used for unknown indication: PFIZER BIONTECH COVID-19 VACCINE (1st dose. lot number FX5095 (Pfizer).) on 13-Feb-2023. Past adverse reactions to the above products included No adverse event with PFIZER BIONTECH COVID-19 VACCINE.    On 27-Sep-2023, the patient received second dose of mRNA-1273.815 (SPIKEVAX 2023-2024) (unknown route) .25 milliliter. On 27-Sep-2023, the patient experienced COVID-19 IMMUNISATION (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.) and INTERCHANGE OF VACCINE PRODUCTS (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.). On an unknown date, the patient experienced NO ADVERSE EVENT (No adverse event). At the time of the report, COVID-19 IMMUNISATION (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.), INTERCHANGE OF VACCINE PRODUCTS (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.) and NO ADVERSE EVENT (No adverse event) outcome was unknown.        For mRNA-1273.815 (SPIKEVAX 2023-2024) (Unknown), the reporter considered NO ADVERSE EVENT (No adverse event) to be not related. No further causality assessments were provided for COVID-19 IMMUNISATION (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.) and INTERCHANGE OF VACCINE PRODUCTS (Pfizer 1st dose was administered on 13Feb2023 and Spikevax 2023 2024 second dose was administered on 27Sep2023.).    Concomitant Medication use information was not provided by reporter.  It was unknown if patient receive any other vaccines in the 4 weeks prior to COVID-19 vaccine.  HCP called to report when they were drawing up the single dose vials for 6 months to 11 years. Patient stated she received the vials yesterday. The vial had 2 doses instead of 1. Patient stated that she knew in the past that a vial could have an overfill. The first vial they draw up had two doses. She wanted to know if she was able to use the remining vials. Caller stated a patient received 0.25 ml dose from the vial and the remining content of the vial was discarded.  Treatment Medication use information was not provided by reporter.