her first dose of the Covid-19 vaccine as it was administered in her back; Intermittent diarrhea; intermittent chills; feeling very tired/fatigue just twice; slight headache; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 84 year-old female patient received bnt162b2 (BNT162B2), administration date 23Feb2021 (Lot number: ER16201) at the age of 84 years as dose 1, single for covid-19 immunisation. Relevant medical history included: "Overactive bladder" (ongoing), notes: diagnosed with an overactive bladder years ago, probably at least 20 years ago, a different medication that was erratic, oxybutynin. Concomitant medication(s) included: MYRBETRIQ taken for hypertonic bladder, start date: Feb2021 (ongoing); OXYBUTYNIN taken for hypertonic bladder. Vaccination history included: Flu shot, administration date: 2020, reaction(s): "sore injection site". The following information was reported: DIARRHOEA (non-serious) with onset 2021, outcome "recovering", described as "Intermittent diarrhea"; CHILLS (non-serious) with onset 2021, outcome "recovered" (2021), described as "intermittent chills"; FATIGUE (non-serious) with onset 2021, outcome "unknown", described as "feeling very tired/fatigue just twice"; HEADACHE (non-serious) with onset 2021, outcome "recovered" (2021), described as "slight headache"; PRODUCT USE ISSUE (non-serious) with onset 23Feb2021, outcome "unknown", described as "her first dose of the Covid-19 vaccine as it was administered in her back".  Additional information: This report was not related to a study or program. Patient took Covid-19 vaccine to prevent from getting Covid. Patient reported that she normally takes Myrbetriq in the morning with food and she began taking Myrbetriq about a month and a half ago. She received samples from her doctor before having the prescription filled. There was no Investigation Assessment. She was calling about the Pfizer Covid-19 vaccine. She weighed herself every morning before showering and her weight ranged between 110 pounds, 111 pounds, 112 pounds, and sometimes 113 pounds, always with a point something. She reported that her physician did not know that she had diarrhea and had been debating calling her physician but figured she would call Pfizer first. She reported that she thinks that the intermittent diarrhea may have began when she had the first dose of the Covid-19 vaccine on 23Feb2021. She was trying to figure it out because she was taking a new medication. She called the pharmacist and asked about side effects of her new medication and the pharmacist reported that there was nothing mentioned about diarrhea as a side effect. She reported that when the diarrhea began, she was wondering if the foods that she was eating and that she went from medications to foods trying to determine the cause of the diarrhea. She did hear or saw something about diarrhea as a side effect of the Covid-19 vaccine. She reported that she was not sure if it was in the sheets given to her when she went to get the vaccine, but that she read about diarrhea being a possible side effect of the Covid-19 vaccine and that her husband heard about diarrhea as a side effect of the Covid-19 vaccine. She reported that the diarrhea had got better in the respect that she didn't think it had been as much diarrhea at one time. She reported that she did not had diarrhea every day and that it was unpredictable. She reported that the Oxybutynin was erratic but did not provide further details. She reported that she took Oxybutynin right up until she went to see her new urologist a month or two ago. She was unable to provide details for Oxybutynin NDC number, lot number, or expiration date as she no longer had the medication. She reported that as fast as the chills come they would go away and they began not too long after her first dose of the Covid-19 vaccine on 23Feb2021. She was unsure about how long she experienced the intermittent chills. She reported that this winter, she felt cold more than any other winter and stated of course she is not getting any younger, even this morning, 08Apr2021, she asked her husband to move her chair into the sun because she was feeling cold in their house. She said that feeling very tired made her nervous because she was active for her age. She experienced fatigue just twice following the first dose of the Covid-19 vaccine on 23Feb2021. She closed her eyes and rest a little bit, then got up and felt much better. She reported that she experienced a slight headache that was on and off after her first dose of the Covid-19 vaccine on 23Feb2021 and she was no longer experiencing the headaches. Time the Vaccination given was between 14:00 and 15:00 and facility type was Clinic set up in gym at (address withheld). Vaccine was not administered at Facility. No requirement to visit an Emergency Room for any AE(s). Not Physician Office prior Vaccinations (within 4 weeks). There were no family Medical History Relevant to AE(s. No relevant tests done.  No follow-up attempts are needed. No further information is expected.