I got very severe reactions; My body was painful all over; very very tired; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  An 80-year-old patient received BNT162b2 (BNT162B2), on 28Apr2022 as dose 4 (booster), single (Lot number: FK9895) at the age of 80 years, in left arm for covid-19 immunisation. The patient's relevant medical history included: "A-fib" (unspecified if ongoing), notes: A-fib (History) which was medicated. Concomitant medication(s) included: AMIODARONE; AMLODIPINE; ELIQUIS. Vaccination history included: Covid-19 vaccine (Primary Immunization series complete, MANUFACTURER UNKNOWN), for COVID-19 Immunization; Covid-19 vaccine (DOSE 3 ( BOOSTER),, unknown manufacturer), for COVID-19 Immunization. The following information was reported: ADVERSE EVENT FOLLOWING IMMUNISATION (non-serious) with onset 29Apr2022, outcome "recovered" (24May2022), described as "I got very severe reactions"; PAIN (non-serious) with onset 29Apr2022, outcome "recovered" (24May2022), described as "My body was painful all over"; FATIGUE (non-serious) with onset 29Apr2022, outcome "recovered" (24May2022), described as "very very tired". The events "i got very severe reactions", "my body was painful all over" and "very very tired" required emergency room visit. Relevant laboratory tests and procedures are available in the appropriate section. Therapeutic measures were taken as a result of adverse event following immunisation, pain, fatigue.  Additional Information: Other Conditions was reported yes. Investigations was reported yes. Other Products was reported Yes. Additional Context: Concern: Consumer stated, "Well patient was calling to report quite serious side effect. Patient had the Pfizer vaccine (COVID-19 vaccine) and patient 80 years old. Patient quite healthy so, Patient do not have any particular underlying conditions other than patient have issue with heart, A-fib (History) which was medicated but other than that was only major health issue Patient have. So Patient received the second booster the 4th dose of Pfizer vaccine on Thursday of 28Apr2022 and about in the middle day on Friday patient got very severe reactions. patient body was painful all over and very very tired and patient called and checked and they said in first couples of days that's possible side effect that occurs but it did not cease after few days and lasted until the day before yesterday. Patient went with concern to see them. First weekend after the shot, second weekend both of the urgent care clinic and they did bunch of the test and all they could determine it was just continued side effects. One of the nurses in the frontline said that it was unusual but its not unheard that a side effect as last long.When requested to probe further: Consumer stated " Patient finally relief from the symptoms but patient wanting report this because it is in data is in your data system." Start date for adverse event: Consumer stated, "The exact date was Friday 29Apr and I received the vaccination on Thursday 28Apr Possibly 14:00 in the afternoon." Lab test: Consumer stated, "patient went to urgent care in had lab test on Saturday, 07May and begin on Sunday, 15May. Patient have lab test done on 25May metabolic panel and extensive bloodwork done both on (voice breaking) to follow to determine if the symptoms definitely having due to the Pfizer vaccine or possibly some other issue and nothing else discovered so primarily appeared it was due to the Pfizer." Treatment: Consumer stated, "The only thing patient took occasionally patient took Tylenol. Patient was very tired patient slept quite a bit in order to reduce (incomplete sentence)."Further assistance: Consumer stated, " Patient was trying to determine if there was other issues which might be related to interaction the Pfizer vaccine and anything else could determine this."