No adverse event; Patient over 65 years old was given today 25May2023 0.25 ml instead of 0.5 ml; This spontaneous case was reported by a pharmacist and describes the occurrence of UNDERDOSE (Patient over 65 years old was given today 25May2023 0.25 ml instead of 0.5 ml) and NO ADVERSE EVENT (No adverse event) in an elderly patient of an unknown gender who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) for COVID-19 prophylaxis.     No Medical History information was reported.    On 25-May-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. On 25-May-2023,  after starting mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)), the patient experienced UNDERDOSE (Patient over 65 years old was given today 25May2023 0.25 ml instead of 0.5 ml). On an unknown date, the patient experienced NO ADVERSE EVENT (No adverse event). At the time of the report, UNDERDOSE (Patient over 65 years old was given today 25May2023 0.25 ml instead of 0.5 ml) 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 UNDERDOSE (Patient over 65 years old was given today 25May2023 0.25 ml instead of 0.5 ml).    Dosage text for suspect product was reported as unknown.  Concomitant drugs were not reported. It was reported that patient had their monovalent and a previous booster dose of bivalent vaccine. Treatment medications were not provided.  This case was reported for elderly patient 1 of 20.   This case was linked to US-MODERNATX, INC.-MOD-2023-726478, US-MODERNATX, INC.-MOD-2023-726492, US-MODERNATX, INC.-MOD-2023-726497, US-MODERNATX, INC.-MOD-2023-726498, US-MODERNATX, INC.-MOD-2023-726499, US-MODERNATX, INC.-MOD-2023-726490, US-MODERNATX, INC.-MOD-2023-726494, US-MODERNATX, INC.-MOD-2023-726502, US-MODERNATX, INC.-MOD-2023-726506, US-MODERNATX, INC.-MOD-2023-726541, US-MODERNATX, INC.-MOD-2023-726538, US-MODERNATX, INC.-MOD-2023-726537, US-MODERNATX, INC.-MOD-2023-726534, US-MODERNATX, INC.-MOD-2023-726545, US-MODERNATX, INC.-MOD-2023-726546, US-MODERNATX, INC.-MOD-2023-726553, US-MODERNATX, INC.-MOD-2023-726521 (E2B Linked Report).   Reporter did not allow further contact; Sender's Comments:  US-MODERNATX, INC.-MOD-2023-726478:Patient no 1 US-MODERNATX, INC.-MOD-2023-726499:Elderly Patient no 7) US-MODERNATX, INC.-MOD-2023-726498:(Elderly Patient no 6) US-MODERNATX, INC.-MOD-2023-726497:(Elderly Patient no 5) US-MODERNATX, INC.-MOD-2023-726492:Elderly Patient no 4) US-MODERNATX, INC.-MOD-2023-726553:(Patient no-11) US-MODERNATX, INC.-MOD-2023-726537:Elderly Patient - 1 US-MODERNATX, INC.-MOD-2023-726545:(Patient no-8) US-MODERNATX, INC.-MOD-2023-726541:Elderly Patient - 1 US-MODERNATX, INC.-MOD-2023-726534:Elderly Patient - 1 US-MODERNATX, INC.-MOD-2023-726506:Patient no - 20 US-MODERNATX, INC.-MOD-2023-726546:(Patient no-9) US-MODERNATX, INC.-MOD-2023-726502:Patient no - 19 US-MODERNATX, INC.-MOD-2023-726490:Elderly Patient - 2 US-MODERNATX, INC.-MOD-2023-726494:Elderly Patient - 3 US-MODERNATX, INC.-MOD-2023-726538:Elderly Patient - 1 US-MODERNATX, INC.-MOD-2023-726521:(Patient no-10)