I mistakenly used sterile water for injection instead of sterile sodium chloride as the diluent for Comirnaty or the Pfizer-BioNTech COVID-19 vaccine./ 3 patients received it.; I mistakenly used sterile water for injection instead of sterile sodium chloride as the diluent for Comirnaty or the Pfizer-BioNTech COVID-19 vaccine./ 3 patients received it.; Pulled the vaccine directly from the freezer, mixed it, and administered it to patients; This is a spontaneous report from a contactable registered nurse. A contactable nurse reported similar events for 3 patients. This is 2 of 3 reports.  A 17-years-old female patient received unknown dose of BNT162B2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE; Lot Number: 30145BA, Expiration Date: 30Nov2021), via an unspecified route of administration on 30Sep2021 at 17:30 (17-year-old at vaccination) as Dose 1, 0.3mL, Single for Covid-19 immunization. The patient received water for injection (STERILE WATER) (manufacturer: Merck) via unspecified route of administration on 30Sep2021 at 17:30 (Batch/lot number: T025911, NDC: 0006-4309-00, Expiration date: 08Mar2023) as unspecified dose and frequency as Diluent for Covid-19 vaccine. Vaccination Facility Type was reported as Clinic and not other facility. The patient's medical history included depression, cannabis use, high cholesterol, uses birth control patch. The patient's concomitant medication(s) included cyanocobalamin (B12-VITAMIN), ascorbic acid, colecalciferol, nicotinamide, panthenol, pyridoxine hydrochloride, retinol palmitate, riboflavin, thiamine hydrochloride, tocopheryl acetate (MULTI VITAMIN), cetirizine hydrochloride (ZYRTEC); guanfacine hydrochloride (INTUNIV) ER, sertraline hydrochloride (ZOLOFT), meningococcal vaccine a/c/y/w conj (dip tox) (MENACTRA) vaccine (manufacturer: Sanofi) administered via unspecified route in left deltoid on 30Sep2021 (Lot number: U7140BA, Expiry Date: 07Nov2022, at age of 17-year-old) as unknown dose and frequency. The report was not related to a study or programme. It was unknown if the patient had received any other vaccine within 4 weeks prior to vaccination. It was unknown if the patient had any other AE(s) following prior to vaccinations. On 30Sep2021, the reporter stated that someone in her facility used an incorrect diluent was mixed with the Pfizer covid vaccine. When sterile water was used instead of sterile sodium chloride. "Patients were involved. It happened last evening. 3 patients received it. Reporter don't had any other details. The reporter mistakenly used sterile water for injection instead of sterile sodium chloride as the diluent for Comirnaty or the Pfizer-BioNTech COVID-19 vaccine/ inadvertent administration of the Pfizer-Biontech Covid19 Vaccine where the vaccine was mixed with a sterile water. She clarified they used sterile water instead of the 0.9% sodium chloride. Queried if the reporter could use the vaccine and if already used to vaccinate individuals, would this count as a valid dose. The reporter was advised that Pfizer had not tested the effects of using sterile water for injection as the diluent for Comirnaty or the Pfizer-BioNTech COVID-19 Vaccine. The diluted vaccine using sterile water for injection as the diluent should be appropriately discarded and not used for vaccination. If the vaccine that was diluted with sterile water for injection was inadvertently administered to individuals, a definitive statement on the quality and usability of the vaccine diluted in water cannot be made. The vaccine had not been tested with sterile water for injection as the diluent. Based on this lack of information, Pfizer was unable to definitively state if the vaccine dose was valid or invalid. The reporter mentioned that she later learned that the vaccine was pulled directly from the freezer, it was a frozen concentrated vaccine mixed with a sterile water and administered it to patients. She wanted to know if there's any different guidance on that and if there are any additional concerned, they need to be aware of. She confirmed this event needed to be added for all three patients, however she doesn't have patient information handy at the time of the call. Advised that there's no additional guidance on the previous information that was provided to reporter. No relevant tests was reported. No investigation assessment was reported. It was unknown if these adverse events resulted in emergency room or physician office visit. Reporter seriousness for used sterile water instead of sterile sodium chloride was considered as Medically significant. Action taken with Sterile water was unknown. The outcome of the events was unknown.  Causality assessment: The causal relationship between BNT162B2 and event sterile water instead of sterile sodium chloride was assessed as unrelated to BNT162B2 by the reporter and Company (BioNTech). The Method of assessment was Global Introspection.  The lot number for the vaccine [BNT162B2] was not provided and will be requested during follow up.; Sender's Comments: Based on the available information, a contributory role of suspect product BNT162B2 to the reported events poor quality product administered and product preparation error was considered unrelated.,Linked Report(s) : US-PFIZER INC-202101301559 same reporter, different patient/event;US-PFIZER INC-202101302701 same reporter, different patient/event