HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.; Vaccine underdose; No adverse event; This spontaneous case was reported by a pharmacist and describes the occurrence of DEVICE LEAKAGE (HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.), UNDERDOSE (Vaccine underdose) and NO ADVERSE EVENT (No adverse event) in a 64-year-old male patient who received mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (batch no. 204F23A) for COVID-19 prophylaxis.    Suspect product included Pre-filled Syringe injection (batch no. 204F23A) for COVID-19 prophylaxis.    No Medical History information was reported.   On an unknown date, the patient received dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (unknown route) 1 dosage form and Pre-filled Syringe (unknown route) at an unspecified dose. On an unknown date, the patient experienced DEVICE LEAKAGE (HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.), UNDERDOSE (Vaccine underdose) and NO ADVERSE EVENT (No adverse event). At the time of the report, DEVICE LEAKAGE (HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.), UNDERDOSE (Vaccine underdose) and NO ADVERSE EVENT (No adverse event) outcome was unknown.        For mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (Unknown), the reporter considered NO ADVERSE EVENT (No adverse event) to be not related. No further causality assessments were provided for DEVICE LEAKAGE (HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.) and UNDERDOSE (Vaccine underdose).  For Pre-filled Syringe, the reporter considered NO ADVERSE EVENT (No adverse event) to be not related. No further causality assessments were provided for DEVICE LEAKAGE (HCP is reporting that they were about to administer a 0.5ml dose of Spikevax from a PFS to a patient and some of the product leaked out.) and UNDERDOSE (Vaccine underdose).    Concomitant medication was not provided. HCP reported that they were about to administer a 0.5ml dose of Spikevax from a PFS syringe to a patient and some of the product leaked out. They did not know what dosage was administered.  Treatment information was not reported.  Device Problem Codes for the event device issue was reported as Device Problem was Fluid Leak.  Rationale for no investigation was reported as after an evaluation of the complaint trend analysis, it is determined that for the present complaint, related to the batch number 204F23A no lot specific trend was identified (See the attached trend Memo). No additional information, pictures or samples were obtained from the complainant after three follow-up emails attempted (see the "Correspondence" section for details). Based on the considerations above, the complaint record will be closed with no further investigation is recommended at this time.   Most recent FOLLOW-UP information incorporated above includes: On 11-Oct-2023: Upon internal review on 30-Oct-2023, non-significant correction performed to update event receipt date. On 23-Oct-2023: Follow-up received include reference section updated. On 20-Nov-2023: Follow-up received is significant. PQC closure report was received and QC comment was added in product tab and in narrative