allergic reaction; an inadvertent 0.3 ml of undiluted Pfizer Covid vaccine given; an inadvertent 0.3 ml of undiluted Pfizer Covid vaccine given; This is a spontaneous report received from a contactable reporter(s) (Physician) from medical information team.  A 28 year-old male patient received bnt162b2 (BNT162B2), intramuscular, administered in deltoid left, administration date 26Aug2021 11:46 (Lot number: EW0185, Expiration Date: Aug2021) at the age of 28 years as dose 1, 0.3 ml single for covid-19 immunisation. Relevant medical history included: "Diabetic" (unspecified if ongoing), notes: Verbatim: patient is a diabetic who is diet controlled. The patient's concomitant medications were not reported. The following information was reported: HYPERSENSITIVITY (non-serious) with onset 26Aug2021, outcome "unknown", described as "allergic reaction"; OVERDOSE (non-serious), PRODUCT PREPARATION ERROR (non-serious) all with onset 26Aug2021, outcome "unknown" and all described as "an inadvertent 0.3 ml of undiluted Pfizer Covid vaccine given". Relevant laboratory tests and procedures are available in the appropriate section.  Additional information: Additional information: physician is the reporter, states that an inadvertent 0.3 ml of undiluted Pfizer Covid vaccine given to a 28-year-old male. (withheld) reports that the patient did experience an allergic reaction while being monitored and is looking for guidance on how to proceed. No diluent, resulting in higher than authorized dose (i.e., 0.3 ml of undiluted vaccine administered) Do not repeat dose Inform the recipient of the potential for local and systemic adverse events. If the administration error resulted in a higher-than-authorized vaccine dose, in general the second dose may still be administered at the recommended interval. However, if local or systemic side effects following vaccination are clinically concerning (outside of the expected side effect profile), lead to serious adverse reactions, or are ongoing at the time of the second dose, the decision to administer the second dose may be assessed on a case-by-case basis. The caller confirms the details provided by the transferring agent, physician reports that his nurse vaccinated the patient with the full dose of the Covid 19 vaccine. The patient had a negative Covid 19 virus test today prior to receiving the Covid 19 vaccine. The doctor who saw the patient was able to convince him to get the Covid 19 vaccine. The nurse who drew up the Covid 19 vaccine from the vial didn't read how to draw it up.  After the vaccine patient observed for 30 minutes, patient figured out that happened and dug the Covid 19 vaccine vial out of the biohazard container, called the nurse, and unfortunately, she did not use the diluent for the Covid 19 vaccine. physician reports the Covid 19 vaccine vial did not come with any package insert. It was just the vial and the diluent in a bag. It had the Aug2021 date on it, so they were using it, then reporter called Pfizer looking for information and guidance since this event occurred. Physician states he will bring the patient back into the office to make sure he's ok. He thought about prescribing Pepcid or an antihistamine or a steroid shot because he knows the patient might feel like hell in about 18 hours. He was told to observe for any adverse reactions and if he sees any he won't give the second dose of Covid 19 vaccine.   No follow-up attempts are possible. No further information is expected.