delayed hypersensitivity to the first dose of the vaccine; allergic reaction; This is a spontaneous report from a contactable pharmacist. An 81-year-old male patient received the first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 MRNA VACCINE; solution for injection; Lot Number: EK9231; Expiration Date: 30Apr2021) intramuscularly on 23Jan2021 (at the age of 81-years-old) at 0.3 mL, single dose for COVID-19 immunization. Medical history and concomitant medications (other products) were both reported as none. On an unspecified date, the patient experienced delayed hypersensitivity to the first dose of the vaccine and allergic reaction. The events were serious for medically significant. Per the reporter, the events required medical intervention by a healthcare professional, so they were more than mild, but they were not life-threatening. The patient's airway was stable and there was no tongue swelling. The course of the events was reported as follows: The patient reported to an outside Emergency Room on 29Jan2021 (also reported as 30Jan2021) with lower lip swelling that eventually progressed to the upper lip and within a day or two it progressed to a localized rash that appeared to be hives on his buttocks. He was diagnosed in the ER with an allergic reaction. The patient was given IM and PO steroids and Benadryl, and the patient did respond to treatment. As of yesterday, the patient had no further symptoms and the reporter guessed that was probably still the case. Per the emergency room the patient went to diagnostics and there were no other potentially causative factors. Per medication review there were no new medications prescribed within the past month. The reporter wanted to know if there was any information on delayed hypersensitivity to the first dose of the vaccine and if the patient should receive his second dose. He wanted to know what the guidance would be on getting the second dose of the COVID vaccine, to see what information Pfizer had regarding documentation with a delayed hypersensitivity reaction to the vaccine. He was also trying to get a sense of the recommendations in this scenario. He did not think that it was anaphylactic, but it was immune mediated and that was his suspicion because IM and oral steroids were effective (in addition to Benadryl) in alleviating this. The clinical outcomes of the events delayed hypersensitivity to the first dose of the vaccine and allergic reaction were both recovered/resolved on an unspecified date after treatment was received. The reporter thought that it was probable or possible that the events were related to BNT162B2 (also reported as unknown). There was a scale they use called the Naranjo scale to determine the likelihood of if a reaction was related to a medication or vaccine and per his score it was possible that the reaction was related but based off his Naranjo score he thought it would be probable but he did not feel that he had enough information and that it would be a very weak probable.  No follow-up attempts are needed. No further information is expected; Sender's Comments: There is a reasonable possibility that the events delayed hypersensitivity and allergic reaction were related to BNT162b2 based on known drug safety profile and temporal relationship.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.