The diarrhea became very bad on 23Mar2021, the day after her second dose of Pfizer-BioNTech Covid-19 Vaccine, time unknown.; She was not feeling well; This is a spontaneous report from a contactable consumer. This 82-year-old female consumer (patient) reported. An 82-year-old female patient received second dose of bnt162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE; Solution for injection; Lot number: not reported), via an unspecified route of administration, administered in right arm shoulder as dose 2, single on 22Mar2021 unknown time in day, morning, maybe noon (at the age of 82-year-old) for covid-19 immunization. Medical history included allergies to weeds and dust in the air but takes like an allergy antihistamine in summertime, so eyes don't itch. The patient previously took first dose of bnt162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE; Solution for injection; Lot number: not reported), via an unspecified route of administration, administered in right arm shoulder as dose 1, single on 01Mar2021 unknown time in day, morning, maybe noon (at the age of 82-year-old) for covid-19 immunization had diarrhoea and weight loss. Concomitant medication included amlodipine at 2.5mg pill twice daily morning and night taken for hypertension from an unspecified start date unknown other than it has been several years. Second dose completed her prescribed therapy. She does not plan to ever get another dose. The vaccine doses were administered at a clinic. Diarrhoea initial onset was on 02Mar2021, the day after her first dose of vaccine, at unknown time, maybe in the morning. The diarrhoea became very bad on 23Mar2021, the day after her second dose of vaccine, time unknown. Patient was not feeling well on 23Mar2021. Finally, the last week in Aug2021 patient does not have diarrhoea any longer. This was after going to the doctor and had many tests done because the doctors said diarrhoea couldn't be a side effect of the vaccine. It was a miserable summer due to the diarrhoea and she spent a lot of money going to doctors to decide why this was going on; but any test they gave her came back negative. Regarding treatment and testing they put her on a diet to see if it could help with diarrhoea: rice, noodles, chicken, fish, applesauce and tea so that wasn't very fulfilling. Patient was back to eating regular food and assumed that she will gain weight back as she no longer has that problem with the diarrhoea. Some days in Mar2021 patient just took a book into the bathroom and stayed there for most of the day because the minute she would leave the bathroom she would have diarrhoea again. During that time, she took over the counter things to stop the diarrhoea and a prescription to stop diarrhoea and the diarrhoea finally stopped. They took breath test to see if she was allergic to or had trouble with fructose or lactose if that was a cause of it. They did a CAT scan of her stomach area to see if there was anything wrong there. Then they checked to make sure that her gallbladder was ok, she had no problem there. They took blood tests, and it all came back ok. There were no findings on those tests, it was all ok, negative. The patient underwent lab tests and procedures which included blood test: negative and computerised tomogram abdomen: negative on unspecified date. At the time of this report, the outcome of event diarrhoea was recovered on unspecified date in Aug2021 and was not feeling well was unknown.  The lot number for BNT162B2 was not provided and will be requested during follow up.