Caller states that since then, he has lost 28 pounds/he saw his doctor last week and he lost 2.5 pounds since seeing his primary 5-7 days; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient.  A 75-year-old male patient received BNT162b2 (BNT162B2), on 07Jan2022 at 13:00 as dose 3 (booster), single (Lot number: FL3198) at the age of 75 years, in left arm for covid-19 immunisation. The patient's family history included: "Hypothyroidism" (unspecified if ongoing), notes: has had Hypothyroidism for quite some time, has been taking medication for the at least twenty years, runs in the family (brother also has same thyroid condition. Concomitant medication(s) included: LEVOTHYROXINE oral taken for hypothyroidism as 88 ug (88mcg tablet once a day by mouth, 6 times a week). Vaccination history included: BNT162b2 (Pfizer covid vaccine first dose: , Lot: EL9262, Expiration: unknown, NDC: unknown), administration date: 27Jan2021, when the patient was 74-year-old, for Covid-19 Immunization; BNT162b2 (Pfizer covid vaccine second dose: 17Feb2021, Lot: EL9266, Expiration: unknown, NDC: unknown), administration date: 17Feb2021, when the patient was 74-year-old, for Covid-19 Immunization. The following information was reported: WEIGHT DECREASED (non-serious) with onset 2022, outcome "unknown", described as "Caller states that since then, he has lost 28 pounds/he saw his doctor last week and he lost 2.5 pounds since seeing his primary 5-7 days". The events "caller states that since then, he has lost 28 pounds/he saw his doctor last week and he lost 2.5 pounds since seeing his primary 5-7 days" required physician office visit. Relevant laboratory tests and procedures are available in the appropriate section.  Additional information: Consumer calling to report adverse event. He received his Pfizer covid booster in Jan2022 and since then he has lost weight, he has lost 28 pounds. He had testing and it has come back fine. He reports he has had many tests, his last colonoscopy was 2 years ago and there was never even a polyp detected. There are numerous things he had done, his blood was tested for so many things, sent three vials of stool samples that gastroenterologist thought was a good idea to do. He has had 8 vials of blood taken for testing between his primary and endocrinologist. He had an endoscopy. He had a recent CT scan recent (within last month) on his chest, abdomen, pelvis, and stomach since his primary was concerned that the weight loss could be a sign of may be cancer. Everything comes back within range or normal. At his age sometimes he forgets things. He takes thyroid medication. His numbers for his thyroid enzymes are right where they should be. Blood tests could be retrieved from his doctor. At his physical in Jan2022 prior to the booster dose he weighed 183 pounds. AE(s) following prior vaccinations were none other than sore arms. States he shouldn't say that. Clarifies His wife and him had covid shots, they had symptoms such as mild headaches and getting dizzy and his primary doctor sent them to get CT scan of their heads to make sure nothing was going on and there was not. This is why his wife decided not to get the booster, but he did get the booster.   No follow-up attempts are possible, no further information is expected.