gas; she had a small stool that was dark, almost black.; severe bloody diarrhea; Diverticulitis; a little achy; Fever; Flu like symptoms; foggy; kind of still weak/She is still a little weak; a knot that is still hot and kind of feverish where she received the vaccine; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 64-year-old female patient received bnt162b2 omi xbb.1.5 (COMIRNATY (2023-2024 FORMULA)), on 28Sep2023 as dose 4 (booster), single (Batch/Lot number: unknown) at the age of 64 years, in left arm for covid-19 immunisation. The patient's relevant medical history included: "Diabetes" (ongoing), notes: Diagnosed many years ago.; "Arthritis" (ongoing), notes: Diagnosed many years ago. Concomitant medication(s) included: INFLUENZA VACCINE taken for immunisation, in Sep2023 as dose number unknown, single. Vaccination history included: bnt162b2 (DOSE 1, SINGLE, Lot: EW0151, Site: Left arm), administration date: 13Apr2021, when the patient was 61-year-old, for COVID-19 immunization; bnt162b2 (DOSE 2, SINGLE, Lot: EW0171, Site: Left arm), administration date: 04May2021, when the patient was 61-year-old, for COVID-19 immunization; bnt162b2 (DOSE 3 (BOOSTER), SINGLE, Lot: F13198, Site: Left arm), administration date: 28Jan2022, when the patient was 62-year-old, for COVID-19 immunization. The following information was reported: VACCINATION SITE WARMTH (non-serious) with onset 2023, outcome "not recovered", described as "a knot that is still hot and kind of feverish where she received the vaccine"; BRAIN FOG (non-serious) with onset Sep2023, outcome "unknown", described as "foggy"; ASTHENIA (non-serious) with onset Sep2023, outcome "not recovered", described as "kind of still weak/She is still a little weak"; INFLUENZA LIKE ILLNESS (non-serious) with onset 29Sep2023, outcome "recovering", described as "Flu like symptoms"; PYREXIA (non-serious) with onset 29Sep2023 at 22:00, outcome "recovered" (30Sep2023), described as "Fever"; DIVERTICULITIS (medically significant) with onset 30Sep2023, outcome "recovering"; PAIN (non-serious) with onset 30Sep2023, outcome "unknown", described as "a little achy"; DIARRHOEA HAEMORRHAGIC (medically significant) with onset 30Sep2023 at 02:00, outcome "recovering", described as "severe bloody diarrhea"; FLATULENCE (non-serious) with onset 02Oct2023, outcome "unknown", described as "gas"; FAECES DISCOLOURED (non-serious) with onset 02Oct2023, outcome "unknown", described as "she had a small stool that was dark, almost black.".  Clinical course details: The patent took the vaccine on Thursday 28Sep2023 and on Friday 29Sep2023, she woke up experiencing a fever and flu like symptoms. Her Fever is currently down. She had a low-grade fever Friday night around 10pm but was resolved by Saturday 30Sep2023. On Saturday morning, 30Sep2023, she contracted diverticulitis and had severe bloody diarrhea. Last year she had that vaccine, and she had no side effects. Her doctor said that there have been reports of this side effect. Her personal opinion is that the vaccine is either contaminated or expired. She called (withheld) and they said the expiration was for next year. Patient stated maybe Pfizer is sending out old vaccines. There was too much bacteria that got into her system or something, that is just common sense. Patient was foggy and kind of still weak. She thinks the weakness came from the diarrhea because she lost so much blood. She was still a little weak and said that she was a little achy, but no longer has a fever. The diarrhea started around 2am on Saturday morning. Yesterday morning on 01Oct2023 was her last bowel movement that was bloody. This morning it seems to be ok, but she had a small stool that was dark, almost black. Patient had a lot of gas. There is a knot that is still hot and kind of feverish where she received the vaccine. She just had a physical less than 2 week ago and everything was good. Patient had medical history of heart condition stated it is not a heart disease. Diagnosed many years ago and was ongoing.  The information on the batch/lot number for bnt162b2 omi xbb.1.5 has been requested and will be submitted if and when received.