Partial clot; has been experiencing pain and aching in his leg; didn't sleep at all that night; heart was feeling weird; having pain in the vein; Venous insufficiency; This is a spontaneous report from a contactable consumer. A 45-year-old male patient received bnt162b2 (PFIZER-BIONTECH COVID-19 VACCINE, Solution for injection, Batch/Lot number was not reported, Expiry date : unknown), dose 2 via an unspecified route of administration, administered in arm right on 27Apr2021 11:15 as dose 2, single for covid-19 immunisation. Medical history included peripheral venous disease from 2019 and ongoing. The patient's concomitant medications was not reported. Historical vaccine of BNT162B2 for COVID-19 immunization on Mar2021 at the age of 45-year-old as per first dose. Prior Vaccination (within 4 weeks prior): None. He has no family medical history, just his personal medical history. He already had venous insufficiency to some degree present but the COVID vaccine made it worse. He was diagnosed in 2019. Caller says that he got the Pfizer COVID vaccine and he is having some little adverse events. He has called a couple doctors today for an appointment to go in and be seen and they all suggested for him to call Pfizer as well. He clarifies that his adverse event is that he has a little bit of venous insufficiency already but it was relatively okay but with both doses of the COVID vaccines, immediately it was like a a switch. As soon as he got the COVID vaccines the situation got much worse for him. He had pain in his leg that felt like a clot for the first week and a half to two weeks after his first dose. Then he got a little bit better, even though he had almost went to the emergency room but he got better after a couple weeks. After his second COVID vaccine, starting that same night, last Tuesday, to now he has been experiencing pain and aching in his leg and he feels like his venous insufficiency went from a 5 to a 10 and it doesn't seem to be getting better so he is going to go see a doctor but they suggested for him to let Pfizer know about this. It was reported that first dose, his pain began the day after he had his COVID vaccine. His second dose was on 27Apr2021 and his 1st dose was 4 weeks before that, so his first dose was either on 30Mar2021 or 31Mar2021. His clarifies that his pain actually began the second day after his first dose. Second dose, the same day of his COVID vaccine, 27Apr2021, he felt pain in his legs and his whole body was flushed and he felt hot. He also didn't sleep at all that night and his heart was feeling weird. He had read that the racing feeling is part of the initial reaction so he had let it go. Then the next couple of days he had felt better and then he started having this feeling of stinging, burning pains in his leg where he knows that vein is, it's his superficial great saphenous vein. He has been having pain in the vein and it has been stinging, burning and aching and he can't sit for more than 20 minutes. He has been exercising every day, drinking water, elevating his leg on the wall to drain it but as soon as he sits again it starts hurting. He feels like it could be a partial blockage but he doesn't really know. He doesn't know if it is actually a partial clot or if it is just his venous insufficiency to such a degree that the fluid pressure inside is making it hurt. It has been this way everyday even though he has been exercising. Honestly, before the COVID vaccine he could exercise and his circulation would be fine that night and for about the next 3 days with no problems but since the COVID vaccine he has been exercising everyday and it doesn't seem to make a difference. He already had a situation but then the vaccine was like a switch and instantly made it worse both times. Probed for 2nd dose outcome and he says that when he is moving around, exercise is the only thing that provides relief, but after that he typically would of been okay for the next few days, but when he gets home from the gym tonight he knows his legs are going to start hurting as soon as he sits down. Even though he sits on his bed and elevates his legs on the wall he knows that as soon as he stands up his legs will start hurting. That's what has happened every day since last Tuesday. Therapy start date populated as Mar2021 since caller is unsure of the exact date of his first COVID vaccine and the therapy stop date populated as the date for his second COVID vaccine. History/ Investigations showed probed for test results, medical conditions or concomitant products and caller says no, there has been nothing out of the ordinary. Anatomical Location of Administration of Pfizer vaccine considered as suspect: right arm for both. No, but he is waiting for the doctor's office to call back him back to schedule for testing. He spoke with them and they said that if it gets worse or continues like it is for another day then he needs to go to the emergency room. The outcome of event pain and aching in his leg was recovered. The outcome of remaining events was unknown.   No follow-up attempts are needed; information about lot/batch number cannot be obtained.