no adverse event; HCP stated she administered the wrong doses to two siblings. She administered the Dark Pink Cap and Label with Yellow Box instead of Dark Blue Cap and Label with Gray Border. Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box.; Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box; This spontaneous case was reported by a physician and describes the occurrence of INCORRECT DOSE ADMINISTERED (HCP stated she administered the wrong doses to two siblings. She administered the Dark Pink Cap and Label with Yellow Box instead of Dark Blue Cap and Label with Gray Border. Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box.), INCORRECT DOSE ADMINISTERED (Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box) and NO ADVERSE EVENT (no adverse event) in a 3-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) for COVID-19 prophylaxis.     HCP did not describe any relevant medical history or conditions. The patient did not receive any other vaccines in the 4 weeks prior to COVID-19 vaccine.     On 24-Apr-2023, the patient received first dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) .2 milliliter. On 24-Apr-2023, the patient experienced INCORRECT DOSE ADMINISTERED (HCP stated she administered the wrong doses to two siblings. She administered the Dark Pink Cap and Label with Yellow Box instead of Dark Blue Cap and Label with Gray Border. Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box.) and INCORRECT DOSE ADMINISTERED (Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box). On an unknown date, the patient experienced NO ADVERSE EVENT (no adverse event). At the time of the report, INCORRECT DOSE ADMINISTERED (HCP stated she administered the wrong doses to two siblings. She administered the Dark Pink Cap and Label with Yellow Box instead of Dark Blue Cap and Label with Gray Border. Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box.), INCORRECT DOSE ADMINISTERED (Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box) 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 assessments were provided for INCORRECT DOSE ADMINISTERED (HCP stated she administered the wrong doses to two siblings. She administered the Dark Pink Cap and Label with Yellow Box instead of Dark Blue Cap and Label with Gray Border. Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box.) and INCORRECT DOSE ADMINISTERED (Patient received 0.2 ml of the Dark Pink Cap and Label with Yellow Box).    No concomitant medication was reported. No treatment medication was reported.  This case contains information about patient 1st out of 2 patients.   This case was linked to US-MODERNATX, INC.-MOD-2023-735146 (E2B Linked Report).; Sender's Comments:  US-MODERNATX, INC.-MOD-2023-735146:same reporter/different patient