No adverse event; Patients received 0.25ml instead of 0.5ml of Bivalent Moderna COVID-19 Booster; This spontaneous case was reported by a pharmacist and describes the occurrence of ACCIDENTAL UNDERDOSE (Patients received 0.25ml instead of 0.5ml of Bivalent Moderna COVID-19 Booster) and NO ADVERSE EVENT (No adverse event) in an adult patient of an unknown gender who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (batch no. 030G22B) for COVID-19 vaccination.     No Medical History information was reported.    In 2022, 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 2022, the patient experienced ACCIDENTAL UNDERDOSE (Patients received 0.25ml instead of 0.5ml of Bivalent Moderna COVID-19 Booster). On an unknown date, the patient experienced NO ADVERSE EVENT (No adverse event). At the time of the report, ACCIDENTAL UNDERDOSE (Patients received 0.25ml instead of 0.5ml of Bivalent Moderna COVID-19 Booster) 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 (Patients received 0.25ml instead of 0.5ml of Bivalent Moderna COVID-19 Booster).    No concomitant medications were reported. 20 patients received 0.25mL instead of 0.5mL of Bivalent Moderna COVID-19 Booster from end of August to middle of October 2022. No treatment information was provided.  This case contains information for the 19th of twenty adult patients as described by the reporter.   This case was linked to US-MODERNATX, INC.-MOD-2022-662849, US-MODERNATX, INC.-MOD-2022-662859, US-MODERNATX, INC.-MOD-2022-662860, US-MODERNATX, INC.-MOD-2022-662863, US-MODERNATX, INC.-MOD-2022-662865, US-MODERNATX, INC.-MOD-2022-662869, US-MODERNATX, INC.-MOD-2022-662871, US-MODERNATX, INC.-MOD-2022-662873, US-MODERNATX, INC.-MOD-2022-662876, US-MODERNATX, INC.-MOD-2022-663016, US-MODERNATX, INC.-MOD-2022-662879, US-MODERNATX, INC.-MOD-2022-662881, US-MODERNATX, INC.-MOD-2022-662958, US-MODERNATX, INC.-MOD-2022-662995, US-MODERNATX, INC.-MOD-2022-663011, US-MODERNATX, INC.-MOD-2022-663016, US-MODERNATX, INC.-MOD-2022-662875, US-MODERNATX, INC.-MOD-2022-662871 (Linked Report).; Sender's Comments:  US-MODERNATX, INC.-MOD-2022-662849:Patient 1 US-MODERNATX, INC.-MOD-2022-662859:Patient 2 US-MODERNATX, INC.-MOD-2022-662860:Patient 3 US-MODERNATX, INC.-MOD-2022-662863:Patient 5 US-MODERNATX, INC.-MOD-2022-662865:Patient 6 US-MODERNATX, INC.-MOD-2022-662869:Patient 8 US-MODERNATX, INC.-MOD-2022-662871:Patient 9 US-MODERNATX, INC.-MOD-2022-662873:Patient 10 US-MODERNATX, INC.-MOD-2022-662876:Patient 12 US-MODERNATX, INC.-MOD-2022-662879:Patient 13 US-MODERNATX, INC.-MOD-2022-662881:Patient 14 US-MODERNATX, INC.-MOD-2022-662958:Patient 15 US-MODERNATX, INC.-MOD-2022-662995:Patient 16 US-MODERNATX, INC.-MOD-2022-663011:Patient 17 US-MODERNATX, INC.-MOD-2022-663016:Patient 18 US-MODERNATX, INC.-MOD-2022-663016:Patient 20 US-MODERNATX, INC.-MOD-2022-662871:Patient 19 US-MODERNATX, INC.-MOD-2022-662875:Patient 19