The patient received the flu vaccine and Pfizer Bivalent vaccine on 07Nov2022; The patient received the flu vaccine and Pfizer Bivalent vaccine on 07Nov2022; upset stomach with nausea and cramping and diarrhea; upset stomach with nausea and cramping and diarrhea; upset stomach with nausea and cramping and diarrhea; upset stomach with nausea and cramping and diarrhea; chills; He hasn't been able to really get out of the bed. He has been weak too; pain all over the body; Muscle ache; the chills are like a seizure almost where his entire body shakes; relapsing fever; This is a spontaneous report received from a contactable reporter(s) (Physician) from medical information team.  A 73-year-old male patient received BNT162b2, BNT162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), on 07Nov2022 as dose 5 (booster), single (Lot number: GJ6665) at the age of 73 years, in arm for covid-19 immunisation; influenza vaccine (FLU VACCINE VII), on 07Nov2022 as dose number unknown, single (Batch/Lot number: unknown), in arm for immunisation. The patient's relevant medical history included: "Atrial fibrillation" (unspecified if ongoing), notes: He has A-fib, atrial fibrillation for which he has a pacemaker implanted. Concomitant medication(s) included: AMLODIPINE; CARVEDILOL; LOSARTAN; FINASTERIDE. Vaccination history included: Covid-19 vaccine (Dose 1), for COVID-19 immunization; Covid-19 vaccine (Dose 2), for COVID-19 immunization; Covid-19 vaccine (Dose 3), for COVID-19 immunization; Covid-19 vaccine (Dose 4), for COVID-19 immunization. The following information was reported: OFF LABEL USE (non-serious), PRODUCT USE ISSUE (non-serious) all with onset 07Nov2022, outcome "unknown" and all described as "The patient received the flu vaccine and Pfizer Bivalent vaccine on 07Nov2022"; ASTHENIA (non-serious) with onset Nov2022, outcome "unknown", described as "He hasn't been able to really get out of the bed. He has been weak too"; MYALGIA (non-serious) with onset Nov2022, outcome "unknown", described as "Muscle ache"; CHILLS (non-serious) with onset Nov2022, outcome "unknown"; PAIN (non-serious) with onset Nov2022, outcome "unknown", described as "pain all over the body"; RELAPSING FEVER (medically significant) with onset Nov2022, outcome "unknown"; SEIZURE (medically significant) with onset Nov2022, outcome "unknown", described as "the chills are like a seizure almost where his entire body shakes"; ABDOMINAL DISCOMFORT (non-serious), NAUSEA (non-serious), MUSCLE SPASMS (non-serious), DIARRHOEA (non-serious) all with onset Nov2022, outcome "unknown" and all described as "upset stomach with nausea and cramping and diarrhea". The patient underwent the following laboratory tests and procedures: Body temperature: 99.5, notes: The fever by the way got up to 99.5. It was a low-grade fever; SARS-CoV-2 antibody test: Negative, notes: I tested him for COVID with the quick test, antibody test at home and he was negative for COVID. Therapeutic measures were taken as a result of relapsing fever, pain, myalgia.  Clinical course: The Physician stated that the patient had initially upset stomach with nausea and cramping and diarrhea and that was the day after the injection and subsequently, so the injection and was on Monday, 07Nov2022. The side effects started 08Nov2022 and then from the 9th until today, he has had what the Physician would call a relapsing fever and chills. They were severe, the chills are like a seizure almost where his entire body shakes and the Physician had to put heating pad and multiple blankets on him and the fever had involved him sweating through all of his clothing and bed linens and kind of dripping in sweat. The fever by the way got up to 99.5. There seemed to be the chills particularly when he attempts to eat anything. All he had been able to keep down was liquid, no solid food. He had pain all over the body, muscle aches. The Physician wanted to report it but mentioned that this was for him the fifth Pfizer. So this was the Pfizer COVID-19 Bivalent vaccine. He was a senior and it was given concurrently with the Flu vaccine on the same arm. The Physician stated that both of his were given on same arm. The Physician gave the patient Advil. The Physician gave him 400 mg for the aches and fever. The fever by the way got up to 99.5. It was a low-grade fever. The Physician had tested the patient for COVID with the quick test, antibody test at home and he was negative for COVID. The Physician wanted to know since this was now the sixth day of the adverse effect, do they have any information about other people who reported similar adverse effects and how long they last. The Physician wanted to know how long they could expect him to remain ill. He hadn't been able to really get out of the bed. He had been weak too, maybe the Physician did mention about weakness but this was the sixth day. So the Physician wanted to know if there was an average link that these adverse effects last.; Sender's Comments: As there is limited information in the case provided, the causal association between the reported events: "Seizure", "Relapsing fever" and the suspect drug BNT162B2 cannot be excluded. The case will be reassessed once new information is available.   The impact of this report on the benefit/risk profile of the Pfizer drug 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.