/the swelling of her knees had diminished greatly; She was quite swollen; She could feel it a little bit in her shins and ankles, however that pain was not acute, she just felt discomfort.; Sore/ she woke up in agony.; She was up all night Friday night and didn't get any sleep at all; Acute bilateral knee pain/ She could feel it a little bit in her shins and ankles, however that pain was not acute, she just felt discomfort.; She began to feel discomfort in her knees; This is a spontaneous report received from contactable consumer, the patient. A 63-year-old adult female received the first dose of intramuscular BNT162b2 (solution for injection; Lot EW0175 and expiry information not provided) as a single dose in the right arm on 06May2021 at 11:40 (at 63-years-old) for COVID-19 immunization. Relevant medical history included Stage IV cancer survivor, mastectomy with removal of lymph nodes (Feb2020-Feb2020), radiation treatment Apr2020-May2020, infusions (ended in 2020), Breast reconstruction with first Tram flap breast reconstruction 05Apr2021 and Full-blown TRAM flap with muscle and fat from abdomen added to breast 13Apr2021, and pain. Concomitant medications included trastuzumab (HERCEPTIN) from unspecified date for unspecified indication; pertuzumab (PERJETA) from unspecified date for unspecified indication; and hydrocodone bitartrate, paracetamol (HYDROCODONE BITARTRATE AND ACETAMINOPHEN) from 20Apr2021 and from 21Apr2021 for pain. The patient previously received prophylaxis with the flu shot, and the tetanus vaccine with which she experienced sore. The patient reported that she received her first dose of the COVID-19 vaccine on Thursday, 06May2021. The next day, 07 May 2021, she woke up in agony with her knees, the pain was acute, she could hardly bare weight. She confirmed the pain was in her knees, but at times she could also feel it a little bit in her shins and ankles, She did try and treat the pain on Friday during the day, maybe about noon on Friday, she took some over-the-counter ibuprofen 200mg. The patient reported that she does not have pain usually, though was shocked when she took two ibuprofen 200mg tablets and the ibuprofen did not even touch the pain, it had no effect whatsoever.  The patient re-iterated that she was administered the first dose of the COVID-19 vaccine on 06May2021 at approximately 11:40AM. Then, the nurse came by, spoke to her, and released her to leave at 11:50-11:55AM. At around 8PM that evening, she began to feel discomfort in her knees. She did not think much of it just through reading info about side effects including achiness and so forth. She went to bed and she slept through the night, which she does not always do. The next day, on 07May2021, she woke up in agony. The patient mentioned that prior to the vaccine, she had been through so many surgeries, so she has a high pain tolerance. The patient explained that she does not even take the pain medication they send home with her. But, with her knees, the pain was acute, she could hardly bare weight. She confirmed the pain was in her knees, but at times she could feel it a little bit in her shins and ankles too, however that pain was not acute, she just felt discomfort. The patient stated that she was up all-night Friday and experienced the pain all day Friday. She told herself to just deal with it and that the pain would get better since she read side effects would dissipate in a couple of days. However, the pain did not, and she was up all-night Friday night and did not get any sleep at all. Saturday morning, on 08May2021, she went to the emergency room (ER). She was seen by an ER physician who immediately put her on IV morphine and steroids and after that, maybe thirty minutes, the pain started easing. She later clarifies she was put on IV dexamethasone and then morphine and ondansetron, stating "maybe that was to wake me up". Caller confirms she has no NDC, Lot number and expiry date for these medications. She confirms she was not admitted into the hospital, she was only there for a couple of hours and then released home with a five-day pack of prednisone. The ER doctor mentioned his colleagues have seen something similar but usually with the second dose. caller explains when the ER doctor examined her, he could see she was quite swollen. She confirms the ER doctor diagnosed her with "acute bilateral knee pain, adverse effects of the COVID-19 vaccine". She came home from the ER and did get some rest. It was to the point now, yesterday she walked around the house and she was not in acute pain at all. She could tell the swelling of her knees had diminished greatly. However, there is still some movement that was uncomfortable, but it was not acute; She confirmed the pain has improved. The patient reported that she did have blood work done in the ER on 08May2021 including C-reactive protein, complete blood count (CBC) with platelet differential, and a comprehensive metabolic panel though results were unknown. The outcome of the events quite swollen/swelling of her knees, sore/ she woke up in agony was recovered on an unspecified date in May2021. The outcome of the events knee pain, discomfort in her knees, feel it a little bit in her shins and ankles, felt discomfort, was recovering. The outcome of the event did not get any sleep at all was unknown.  Information on Lot/Batch number was available. Additional information has been requested.