About a month I after I received the second dose, I got a huge bakers cyst behind my knee.; Fluid build up behind the knee and above which causes limitation in daily activities and pain; This is a spontaneous report received from contactable reporter(s) (Pharmacist). The reporter is the patient.  A 45-year-old female patient (not pregnant) received BNT162b2 (BNT162B2), on 19Jan2021 at 15:00 as dose 2, single (Lot number: Ej1686) at the age of 46 years, in right arm for covid-19 immunisation. The patient's relevant medical history was not reported. The patient took concomitant medications. Vaccination history included: BNT162b2 (dose 1, Single, lot number-El0140, time-03:00 AM, location-Left arm), administration date: 29Dec2020, for Covid-19 immunisation. The following information was reported: SYNOVIAL CYST (disability) with onset 24Feb2021, outcome "not recovered", described as "About a month I after I received the second dose, I got a huge bakers cyst behind my knee."; LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (disability) with onset 24Feb2021, outcome "not recovered", described as "Fluid build up behind the knee and above which causes limitation in daily activities and pain". The events "about a month i after i received the second dose, i got a huge bakers cyst behind my knee." and "fluid build up behind the knee and above which causes limitation in daily activities and pain" required physician office visit. The patient underwent the following laboratory tests and procedures: Magnetic resonance imaging: Unknown results; X-ray: Unknown results. Therapeutic measures were taken as a result of synovial cyst, loss of personal independence in daily activities. Ae treatment was steroid pack, steroid injections and fluid drainage.  Clinical course: Facility type vaccine: Pharmacy or Drug Store. Patient was not given any vaccine in four weeks. Other medications were given in two weeks.About a month after she received the second dose, she got a huge bakers cyst behind her knee. A steroid did not help. She went to an orthopedic doctor who did an X-ray and MRI on that day. She needed 20 times drained from behind her knee and 12 cc from above her knee. She had continued to struggle until the present time with knee issues. Fluid build up behind the knee and above which caused limitation in daily activities and pain. It was affecting her quality of life and interfering with her work since she was required to stand 12 hours a shift. She was slated to have injections in her knee to help increase synovial fluid. She was only 47 and it was greatly affecting her life. She was just looking really for answers or a solution so she could go back to her normal activities with minimal to no pain.; Sender's Comments: Based on the current available limited information in the case provided, the causal association between the events synovial cyst, activities of daily life impaired and the use of suspect product cannot be fully excluded. The impact of this report on the benefit/risk profile of the Pfizer product 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