diarrhea/ Loose Stools; this dose as her fifth updated Pfizer covid vaccine, received 07Sep2022; 5th Booster Dose, received 07Sep2022; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team, Program ID. The reporter is the patient.  A 91-year-old female patient received BNT162b2, BNT162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), on 07Sep2022 as dose 5 (booster), single (Lot number: GH9694) at the age of 91 years for covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. Vaccination history included: BNT162b2 (DOSE 1, SINGLE, Lot: EL9262, She read from the vaccine card: MSB1-NZ), administration date: 23Jan2021, when the patient was 89-year-old, for COVID-19 immunization, reaction(s): "sore in her arm"; BNT162b2 (DOSE 2, SINGLE, Lot: FM9810, She read from the vaccine card: MSBI then something after it but cannot make out what it is, might be a O or Q after MSBI.), administration date: 13Feb2021, when the patient was 89-year-old, for COVID-19 immunization, reaction(s): "sore in her arm"; BNT162b2 (DOSE 3 (BOOSTER), SINGLE, Lot: FA7485), administration date: 25Aug2021, when the patient was 90-year-old, for COVID-19 immunization, reaction(s): "sore in her arm"; BNT162b2 (DOSE 4 (BOOSTER), SINGLE, Lot: FK9893  OR FH9893 , think it may be a K for second digit.), administration date: 31Mar2022, when the patient was 90-year-old, for COVID-19 immunization, reaction(s): "sore in her arm". The following information was reported: IMMUNISATION (non-serious) with onset 07Sep2022, outcome "unknown", described as "5th Booster Dose, received 07Sep2022"; DIARRHOEA (non-serious) with onset 07Sep2022, outcome "recovering", described as "diarrhea/ Loose Stools"; OFF LABEL USE (non-serious) with onset 07Sep2022, outcome "unknown", described as "this dose as her fifth updated Pfizer covid vaccine, received 07Sep2022". Therapeutic measures were taken as a result of diarrhoea.  Clinical course: she had diarrhea since that 5th dose and that it started within 2 hours of having that dose and was severe the 4th day and getting less severe, still a watery stool. Pharmacist said she could take Imodium or it would go away on its own. She had 6 more episodes of diarrhea and by that time it was the next day and so she started taking Imodium. The Imodium helped a bit but the diarrhea still continued. Then she started taking Pedialyte and diarrhea is getting somewhat better. Still has loose stool but not as much of it that it was earlier. She is going to see her doctor at 330 this afternoon. She wants to know if the vaccination she received will still be effective after all of this, since it has been 4 days. no information about duration of diarrhea, many side effects only lasted 1-2 days on average. Directed back to HCP for treatment recommendations. This report is not related to a study or programme. Patient brought up concerns about the handling of the vaccination, stating, "the vaccination was given in the whole general area, the person giving it was carrying it around in a jug. Description of complaint: She wants to know if the vaccination she received will still be effective after all of this, since it has been 4 days. The Imodium helped a bit but the diarrhea still continued. She declines to provide details for Imodium. Requests to be transferred for her question. Declines to continue with report. In addition, the caller mentioned that she's gotten all of her vaccinations and booster from Pfizer and never had any reaction except a sore in her arm, and this is the first time experienced a severe reaction.  Follow-up attempts are completed. No further information is expected.