This case involves an unknown age male patient whose nurse diluted the YF (Yellow fever)-vaccine with sterile water instead of the 0.6ml normal saline, with no reported adverse event and nurse injected the patient IM instead of subq as indicated, with no reported adverse event while receiving vaccine YELLOW FEVER VACCINE - US [YF-VAX]. The patient's past medical history, medical treatment(s), and family history were not provided. Concomitant medications included MEASLES VACCINE, MUMPS VACCINE, RUBELLA VACCINE (MMR) for Immunisation; TYPHOID VACCINE POLYSACCH VI (TYPHOID VACCINE POLYSACCH VI) for Immunisation; and MENINGOCOCCAL VACCINE A/C/Y/W CONJ (CRM197) (MENVEO) for Immunisation. On 17-Dec-2021, the patient received 0.5ml total dose of suspect YELLOW FEVER VACCINE - US (lot number not reported formulation Solution for injection and strength: standard) via intramuscular route in the right deltoid for prophylactic vaccination. On 17-DEC-2021 the patient developed a non-serious event, "nurse diluted the yf-vaccine with sterile water instead of the 0.6ml normal saline, with no reported adverse event" (Product preparation issue) (latency: same day) following the administration of YELLOW FEVER VACCINE - US. On 17-DEC-2021 the patient developed a non-serious event, "nurse injected the patient im (intramuscular) instead of subq (sub-cutaneous) as indicated, with no reported adverse event" (incorrect route of product administration) (latency: same day) following the administration of YELLOW FEVER VACCINE - US. It was reported, "patient's get their vaccines from the injection clinic on 17Dec2021, however in this instance, the male patient received the YF-Vaccine from the doctor's clinic. Only the box of the vaccine was in the clinic and not the vaccine and the diluent, so the nurse diluted the YF-vaccine with sterile water instead of the 0.6mL normal saline and injected the patient IM instead of SubQ as indicated. She asks if the dose was a valid dose. Caller asks how far apart the YF vaccine and the COVID vaccine should be." Action taken with YELLOW FEVER VACCINE (YF-VAX) was not applicable. It was not reported if the patient received a corrective treatment for the events. At time of reporting, the outcome was Unknown for the event nurse diluted the yf-vaccine with sterile water instead of the 0.6ml normal saline , with no reported adverse event and was Unknown for the event nurse injected the patient IM (intramuscular) instead of subq (subcutaneous) as indicated, with no reported adverse event. This suspected adverse reaction report is submitted and classified as a medication error solely and exclusively to ensure the marketing authorization holder's compliance. The classification as a medical error is in no way intended, nor should it be interpreted or construed as an allegation or claim made by the marketing authorization holder that any third party has contributed to or is to be held liable for the occurrence of this medication error. Additional information was received on 20-Dec-2021 from other health care professional: event linking for nurse diluted the YF-vaccine with sterile water instead of the 0.6ml normal saline , with no reported adverse event was updated; concomitants added. Text amended accordingly.