Severe Diarrhea; he has some rumbling in there; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 68 year-old male patient received BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE), administered in arm right, administration date 16Mar2021 16:30 (Lot number: EN6198) at the age of 68 years as dose 1, single for COVID-19 immunisation. Relevant medical history included: "Magnesium deficiency", start date: Oct2020 (ongoing); "Fatty Tissue on Brain", start date: 2017 (ongoing), notes: Diagnosed 4 years ago; "Arrhythmia", stop date: Sep2020, notes: diagnosed 6 years ago when diagnosed with a heart murmur that progressed; "Open heart surgery", start date: Sep2020, stop date: Sep2020, notes: fixed a leaky valve; "High blood pressure" (ongoing), notes: diagnosed don't recall exactly he would say maybe 4-5 years ago; "Diabetes", start date: Sep2020 (ongoing), notes: diagnosed with prediabetes 10 years ago; "Diuretic" (unspecified if ongoing), notes: Verbatim: Diuretic; "cardio myopathy" (unspecified if ongoing); "surgical ablation" (unspecified if ongoing); "Blood Thinning/blood clots" (ongoing). Concomitant medication(s) included: ASPIRIN (E.C.) taken for thrombosis, start date: Sep2020 (ongoing); SPIRONOLACTONE taken for blood pressure measurement, diuretic therapy, start date: Sep2020 (ongoing); MAGNESIUM OXIDE taken for magnesium deficiency, start date: Oct2020 (ongoing); ROSUVASTATIN taken for cerebral disorder, start date: 2017 (ongoing); METOPROLOL TARTRATE taken for arrhythmia, start date: Sep2020 (ongoing); CLONIDINE HYDROCHLORIDE (ongoing); ELIQUIS taken for thrombosis, start date: 2018 (ongoing); JARDIANCE taken for diabetes mellitus, start date: Sep2020 (ongoing); OZEMPIC taken for diabetes mellitus (ongoing). The following information was reported: DIARRHOEA (non-serious) with onset 17Mar2021 05:00, outcome "recovering", described as "Severe Diarrhea"; GASTROINTESTINAL SOUNDS ABNORMAL (non-serious) with onset 17Mar2021 05:00, outcome "recovering", described as "he has some rumbling in there". Therapeutic measures were taken as a result of diarrhoea, gastrointestinal sounds abnormal.  Additional information: The patient had no relevant family medical history. The patient had no prior vaccinations. The patient had no history of previous immunization with the Pfizer vaccine considered as suspect. The patient did not receive additional vaccines administered on same date of the Pfizer suspect. The patient's concomitant medications also included multivitamins (bounty fresh) for supplementation. The vaccine was administered in a hospital. Clinical course: The patient received the vaccine a week ago Tuesday and somewhere in middle of night toward Wednesday he started experiencing severe diarrhea for three days and nothing that he took seemed to stop it. He stated that lasted until Friday, Saturday and Sunday he was fine and then on Monday it reoccurred and lasted until last night. He seemed okay today, he woke up fine although he had some rumbling in there but it had not turned to diarrhea at this point but he did not know that it was gone yet. The events did not result to emergency or physician office visit. The patient was treated with Imodium and Kaopectate for the events. His doctor told him to double up on the doses, even if it only says take so many milligrams a day to do it anyway.   No follow-up attempts are possible. No further information is expected.