Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride; No adverse event; Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride; This spontaneous case was reported by a pharmacist and describes the occurrence of PRODUCT PREPARATION ERROR (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride), POOR QUALITY PRODUCT ADMINISTERED (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride) and NO ADVERSE EVENT (No adverse event) in a 4-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (batch no. 215K22A) for COVID-19 prophylaxis.     Previously administered products included for COVID-19 prophylaxis: Moderna COVID-19 Vaccine (Patient received Moderna primary series on unknown date). Past adverse reactions to the above products included No adverse event with Moderna COVID-19 Vaccine.    On 04-Jan-2023, the patient received dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) .2 milliliter. On 04-Jan-2023,  after starting mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)), the patient experienced POOR QUALITY PRODUCT ADMINISTERED (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride). On an unknown date, the patient experienced PRODUCT PREPARATION ERROR (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride) and NO ADVERSE EVENT (No adverse event). At the time of the report, PRODUCT PREPARATION ERROR (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride), POOR QUALITY PRODUCT ADMINISTERED (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride) 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 PRODUCT PREPARATION ERROR (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride) and POOR QUALITY PRODUCT ADMINISTERED (Vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride).    Concomitant product information was not provided by the reporter.   Patient didn't received any other vaccines in the 4 weeks prior to COVID-19 vaccine.  Patient was supposed to get the toddler Moderna bivalent, but the vaccine provider diluted the bivalent booster (for 6m-5y) with 2.2 ml of sterile water instead of sodium chloride. Reporter wants to know if there any further recommendation on that and 0.2 ml of that dilution was given to the patient on 04-Jan-2023. The pharmacist was used to giving Pfizer doses, so they diluted the Moderna bivalent booster.   Treatment information was not provided.