No adverse event; HCP stated they accidentally administered 25 booster doses of 0.25 mL of Moderna COVID-19 Vaccine Bivalent between 26AUG2023 and 27AUG2023 to adult patients, instead of the usual 0.5 mL dosage; This spontaneous case was reported by an other health care professional and describes the occurrence of ACCIDENTAL UNDERDOSE (HCP stated they accidentally administered 25 booster doses of 0.25 mL of Moderna COVID-19 Vaccine Bivalent between 26AUG2023 and 27AUG2023 to adult patients, instead of the usual 0.5 mL dosage) and NO ADVERSE EVENT (No adverse event) in a 53-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (batch no. AS7664B) for COVID-19 prophylaxis.     No Medical History information was reported.    In August 2023, the patient received dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) .25 milliliter. In August 2023, the patient experienced ACCIDENTAL UNDERDOSE (HCP stated they accidentally administered 25 booster doses of 0.25 mL of Moderna COVID-19 Vaccine Bivalent between 26AUG2023 and 27AUG2023 to adult patients, instead of the usual 0.5 mL dosage). On an unknown date, the patient experienced NO ADVERSE EVENT (No adverse event). At the time of the report, ACCIDENTAL UNDERDOSE (HCP stated they accidentally administered 25 booster doses of 0.25 mL of Moderna COVID-19 Vaccine Bivalent between 26AUG2023 and 27AUG2023 to adult patients, instead of the usual 0.5 mL dosage) and NO ADVERSE EVENT (No adverse event) outcome was unknown.        For mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (Unknown), the reporter considered NO ADVERSE EVENT (No adverse event) to be not related. No further causality assessment was provided for ACCIDENTAL UNDERDOSE (HCP stated they accidentally administered 25 booster doses of 0.25 mL of Moderna COVID-19 Vaccine Bivalent between 26AUG2023 and 27AUG2023 to adult patients, instead of the usual 0.5 mL dosage).    This case contains information for patient 01 out of 25. No concomitant medication information was reported. Patient did not receive any other vaccines in the 4 weeks prior to COVID-19 vaccine. No adverse events were reported for any of the patients. No treatment information was reported.   This case was linked to US-MODERNATX, INC.-MOD-2023-738775, US-MODERNATX, INC.-MOD-2023-738782, US-MODERNATX, INC.-MOD-2023-738783, US-MODERNATX, INC.-MOD-2023-738786, US-MODERNATX, INC.-MOD-2023-738787, US-MODERNATX, INC.-MOD-2023-738788, US-MODERNATX, INC.-MOD-2023-738791, US-MODERNATX, INC.-MOD-2023-738792, US-MODERNATX, INC.-MOD-2023-738797, US-MODERNATX, INC.-MOD-2023-738800, US-MODERNATX, INC.-MOD-2023-738805, US-MODERNATX, INC.-MOD-2023-738807, US-MODERNATX, INC.-MOD-2023-738813, US-MODERNATX, INC.-MOD-2023-738811, US-MODERNATX, INC.-MOD-2023-738815, US-MODERNATX, INC.-MOD-2023-738816, US-MODERNATX, INC.-MOD-2023-738821, US-MODERNATX, INC.-MOD-2023-738825, US-MODERNATX, INC.-MOD-2023-738830, US-MODERNATX, INC.-MOD-2023-738832, US-MODERNATX, INC.-MOD-2023-738802, US-MODERNATX, INC.-MOD-2023-738835, US-MODERNATX, INC.-MOD-2023-738839, US-MODERNATX, INC.-MOD-2023-738845 (Linked Report).   Most recent FOLLOW-UP information incorporated above includes: On 29-Aug-2023: Live follow-up contains significant information which included Patient age, initials, gender, and new references were added.; Sender's Comments:  US-MODERNATX, INC.-MOD-2023-738775:Patient 2 US-MODERNATX, INC.-MOD-2023-738783:patient 16 US-MODERNATX, INC.-MOD-2023-738782:Patient 3 US-MODERNATX, INC.-MOD-2023-738787:Patient 17 US-MODERNATX, INC.-MOD-2023-738786:Patient 4 US-MODERNATX, INC.-MOD-2023-738792:Patient 18 US-MODERNATX, INC.-MOD-2023-738791:Patient 6 US-MODERNATX, INC.-MOD-2023-738788:Patient 5 US-MODERNATX, INC.-MOD-2023-738797:Patient 19 US-MODERNATX, INC.-MOD-2023-738805:Patient 20 US-MODERNATX, INC.-MOD-2023-738800:Patient 7 US-MODERNATX, INC.-MOD-2023-738813:Patient 11 US-MODERNATX, INC.-MOD-2023-738807:Patient 8 US-MODERNATX, INC.-MOD-2023-738816:Patient 12 US-MODERNATX, INC.-MOD-2023-738815:Patient 10 US-MODERNATX, INC.-MOD-2023-738811:Patient 9 US-MODERNATX, INC.-MOD-2023-738821:Patirnt 13 US-MODERNATX, INC.-MOD-2023-738825:Patient 14 US-MODERNATX, INC.-MOD-2023-738830:Patient 15 US-MODERNATX, INC.-MOD-2023-738832:Patient 22 US-MODERNATX, INC.-MOD-2023-738802:Patient 21 US-MODERNATX, INC.-MOD-2023-738835:Patient 23 US-MODERNATX, INC.-MOD-2023-738839:Patient 24 US-MODERNATX, INC.-MOD-2023-738845:Patient 25