severe diarrhea; woke up  feeling bad; blood pressure was 105/55 with a PR of 132; blood pressure was 105/55 with a PR of 132; the patient also received FLUZONE on the same day as the vaccination date; the patient also received FLUZONE on the same day as the vaccination date; This is a spontaneous report from a contactable healthcare professional (patient). An 82-year-old male patient received BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, solution for injection, lot number: FF8841), via an unspecified route of administration, administered in the left arm on 27Sep2021 15:00 (at the age of 82 years old) as dose 3 (booster), single for COVID-19 immunization; and influenza vaccine (FLUZONE; manufacturer: Sanofi Pasteur, lot number: UJ716AA), via an unspecified route of administration at the left arm on 27Sep2021, at dose 1, single for immunization. Medical history included high cholesterol from an unknown date and unknown if ongoing. The patient did not have COVID prior to the vaccination. There were no known allergies. Concomitant medications included finasteride, levothyroxine sodium (LEVOTHYROXIN), sertraline and simvastatin, all taken for unspecified indications, start and stop dates were not reported. The patient previously received BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, solution for injection), via an unspecified route of administration, administered in the left arm on 29Jan2021 12:00 (at the age of 81 years old; lot number: EN5318) as dose 1, single and via an unspecified route of administration, administered in the left arm on 19Feb2021 12:00 (at the age of 81 years old; lot number: LN5518) as dose 2, single for COVID-19 immunization. The patient experienced severe diarrhea, woke up feeling bad, blood pressure was 105/55 with a PR of 132 on 28Sep2021. It was reported that the next day, on 28Sep2021, the patient began to have severe diarrhea and he woke up feeling bad. He checked his blood pressure and it was 105/55 with a PR of 132. He went to the emergency room at a cardiovascular center. They gave him one unit of saline drip and his BP returned to normal. They kept him for observation overnight. They tested him for all kinds of infections, and they were all negative. He went home and began using loperamide to try to control his diarrhea. The diarrhea continued and last Friday, he switched to Peptobismal and the BRAT diet. It has not controlled his diarrhea. He has no fever, aches, pains, nor any signs of other disease. His temperature was normal, and his BP and HR are normal. Consistently about 120/65 and PR 55. All events resulted in emergency room/department or urgent care. The reporter assessed all events as serious [life threatening illness (immediate risk of death from the event)]. It was also reported that the patient also received Fluzone on the same day as the vaccination date on 27Sep2021. The patient underwent lab tests and procedures which included blood pressure: 120/65 on an unspecified date in 2021 and 105/55 on 28Sep2021, laboratory test: negative on an unspecified date in 2021, body temperature: normal on an unspecified date in 2021, pulse rate: 55 on an unspecified date in 2021 and 132 on 28Sep2021, and COVID-19 virus test: negative on 05Oct2021. The outcome of the events severe diarrhea, woke up feeling bad was not recovered while the outcome of all other events was recovering.; Sender's Comments: Based on the available information in the case the causal association between the events diarrhoea, feeling abnormal, blood pressure diastolic decreased, heart rate increased and the suspect drug BNT162B2 cannot be excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.