Fever; confirmed he he has Mono; left sided abdominal pain; This is a spontaneous report received from a contactable reporter(s) (Other HCP) from medical information team.  A 51 year-old male patient received bnt162b2 (BNT162B2), administered in deltoid right, administration date 05Aug2021 13:30 (Lot number: EW0172) at the age of 51 years as dose 1, single for covid-19 immunisation. Relevant medical history included: "Mono" (unspecified if ongoing), notes: He had this about 6-7 years ago. The patient's concomitant medications were not reported. The following information was reported: PYREXIA (non-serious) with onset 15Aug2021, outcome "not recovered", described as "Fever"; INFECTIOUS MONONUCLEOSIS (non-serious) with onset Aug2021, outcome "unknown", described as "confirmed he he has Mono"; ABDOMINAL PAIN (non-serious) with onset Aug2021, outcome "unknown", described as "left sided abdominal pain". The events "fever" and "confirmed he he has mono" were evaluated at the physician office visit. Relevant laboratory tests and procedures are available in the appropriate section. Therapeutic measures were taken as a result of pyrexia, infectious mononucleosis.  Additional information: Events pyrexia and Infectious mononucleosis did not required emergency room visit. Patient did not received any vaccine within 4 weeks prior to the to the first administration date of the suspect vaccine. There were no family medical history relevant to AE(s). The caller stated that her husband received his 1st dose almost 3 weeks ago and is due to get his 2nd dose on Thursday (Further clarified as 26Aug2021). 10 days after receiving his 1st dose he developed a fever. They just found out yesterday that he has Mono, which he had in the past. Caller states that she is not going to let him get the 2nd dose on Thursday because he still had a fever last night. She wants to know when is the appropriate time for him to get the 2nd dose. States that she did talk to his doctor and a pharmacist regarding the vaccine getting far enough in his system to bring the Mono back up, or cause it to reoccur, and they thought that it was possible, but she has been trying to do research on it and can't find anything. States that he doesn't want to get the 2nd dose, and she doesn't want him to go through a multi-system organ failure. She just wishes that there was more information out there so that they knew that this was a possibility. Caller states that today he had fever, he had fever for 9 days. Last fever was this morning. His fever was really high at one point, up to 104, but is getting lower, though he still has it every day. States that he is getting better, but they learned last time he had it that Mono lasts forever for him. Over the weekend he had a fever up to 104 and she was concerned about that especially because he also had left sided abdominal pain, so she was worried about his spleen. States that he was taking Tylenol and Ibuprofen for the fever and that got him through it. Causality: States that she doesn't know for certain that this was caused by the Covid 19 vaccine, but she does know that it can bring you down a little bit. States that the doctor and pharmacist she spoke with did say that it was possible that this was caused by the vaccine. The vaccine does cause an inflammatory process and cause the glands to swell. States that she had to reschedule her mammogram because it's not recommended to get a mammogram within 4-6 weeks after getting the vaccine because it can show enlarged lymph nodes.  No follow-up attempts are possible. No further information is expected.