Allergic reaction / high reaction to vaccine; Had concerns while hospitalized on 07Mar2021 that she could have the Delta variant of the Covid 19 virus; Definitely neurological; left sided weakness; Whole left leg was slipping out from under her; Oxygen levels very low / on oxygen; Temperature 103.5 degrees Fahrenheit / temperature would shoot up later in the afternoon around dinner time and late in the morning; Was confused and there were things that she didn't know like what day it was; Unable to stand; This is a spontaneous report received from a contactable consumer or other non-health care professional (patient). A 74-year-old female patient received first dose of bnt162b2 (PFIZER-BIONTECH COVID-19 VACCINE, Formulation: solution for injection, Lot Number: unknown) via an unspecified route of administration, administered in arm left on 06Mar2021 at 14:00 (at the age of 73-years-old) as DOSE 1, SINGLE for COVID-19 immunisation. Medical history included rheumatoid arthritis, knee replacement, hip replacement and breast cancer from an unknown date and unknown if ongoing, sars-cov-2 test positive from 29Dec2020 to an unknown date (she tested positive for the Covid 19 virus on 29Dec2020), pneumonia (positive for the Covid 19 virus on 29Dec2020 and 8 days later she got pneumonia, with pneumonia she was given Prednisone) from an unknown date and unknown if ongoing. Concomitant medications were not reported. Reporter had a patient on the line who was calling to order some medication but mentioned the patient had her first and second Covid 19 vaccines and she had some side effects and she felt like she might be allergic to it. She stated her doctor told her she had an allergic reaction to the Covid 19 vaccine. Her rheumatologist told her she had a high reaction to the Covid 19 vaccine. None of her doctor's including her primary care, rheumatologist, and neurologist had seen side effects from the Covid 19 vaccine like she had. She did some research online and read saw that a small percentage of people, may be 1.6 percent of people had left sided weakness from the Covid 19 vaccine which was exactly what she had on 07Mar2021. When asked if the caller had reported this before she stated that she had a lot going on and it was hard for her to keep track of everything because she just moved into a new house 3 weeks ago and she had a lot of doctors appointments. She thought her doctor at (hospital) might had reported her experience. Her pulmonary doctor was involved too because her oxygen levels were very low. She reported that her first Covid 19 vaccine was the worst dose. She got her first dose on 06Mar2021 at which is a big hospital in at 2:00 PM. She came home felt fine, had dinner, felt fine and she took her normal medications because she was told to continue taking her normal medications as she did every night. She woke up the next morning on 07Mar2021 on a sunday and she was trying to get out of bed but her whole left leg was slipping out from under her. She was staying with her son so she called out for him and he had to pull her up and hold onto her and walk her to the bathroom so she could go. He took her temperature and it was 103.5 degrees fahrenheit. Her son called 911 and emergency medical services came to her in the bathroom, listened to her symptoms, heartrate and told her she would be transported to the hospital. Her son helped her get dressed. She had 3 flights of stairs so she was helped down to the middle floor then put on a gurney and she was carried down to the ground level and put in the ambulance. She was hooked up to an EKG and that was ok. She was confused and there were things that she didn't know, like what day it was. She was taken to the emergency department and the emergency department was full so she had to wait for a room. She had an MRI of her brain to check for blood clots and there were no blood clots. Her room was then open and she was given tylenol and her temperature went down to 101 degrees fahrenheit. Her temperature would shoot up later in the afternoon around dinner time and late in the morning. She had some blood tests done and labs and those were fine and her urine was fine. She stated it was definitely neurological. She stated she had the Covid 19 virus around christmas time 2020. She did have an autoimmune disease so she can get sick really quick. While in with pneumonia she was given prednisone. She reported that she was admitted to hospital on 07Mar2021 and stayed for 5 days after receiving the first dose of the Covid 19 vaccine. When discharged she had a normal temperature and she had more strength on the left side. She was unstable in her walking because of her medical history and surgeries. Hospital had an at home hospital assistance program. A medic came every morning and checked her over and made her walk up the stairs and checked her oxygen. The medic would relay his findings to her doctor. She was also sent home on oxygen. She was given a little kit from the hospital that had an oxygen finger reader for her oxygen levels, a thermometer, an albuterol inhaler if she needed it, and a blood pressure cuff. The hospital outpatient doctor would also talk to her and see how she was doing. She stayed 5 days hospital after the Covid 19 vaccine. She was admitted on 07Mar2021 and discharged on 11Mar2021. She had concerns while hospitalized on 07Mar2021 that she could have the delta variant of the Covid 19 virus. Covid 19 virus cases in had begun to climb because people were not wearing masks but the doctor told her there was no way to test for the delta variant. Her doctor told her she did not have the delta variant of the Covid 19 virus. Her doctor told her that her symptoms were an allergic reaction to the Covid 19 vaccine that she had received on 06Mar2021. She has an autoimmune disease and she can get viruses pretty rapidly. She waited until she was a lot stronger and decided to get the second dose of the Covid 19 vaccine on 30Jul2021. She states that her primary care doctor and her pulmonologist and her neurologist told her they had never heard of anyone with the severe left sided weakness and high fever and confusion and being unable to stand after getting a Covid 19 vaccine. She received both Covid 19 vaccines in her left arm because in Jun2020 she had breast cancer surgery and she was a limb alert for her right arm. Nothing could be taken or withdrawn from her right arm. She provided the following information historically from her time with the Covid 19 virus in Dec2020. She stated after she got the pneumonia from the Covid 19 virus she had to wait to get stronger. She was prescribed steroids because she had lung congestion and a heaviness in her breathing. She developed the pneumonia 8 days after she was positive with the Covid 19 virus. Her doctor advised once she was stronger she needed to get the pneumonia booster. He also advised her to get the Covid 19 vaccine once she was stronger. She had prednisone, albuterol and another treatment but she cannot remember the name of it. It was something she had to pour into a cup and turn on a machine and there would be an inhalant coming out and she would have to breathe it in until the cup was empty. She tried to look up what happened to her because she was feeling like an odd duck. She was online and she was searching side effects from the pfizer covid 19 vaccine like left sided weakness and high fever and she did find a couple reports. One was from another country. It was reported that some people had exactly what she had as far as her side effects. She also saw that some people had what she had. She stated it was a small percentage but there were reports. Her primary care doctor, her pulmonologist, and the hospitalist had never heard of left sided weakness after getting the Covid 19 vaccine. Maybe it was because the Covid 19 vaccine was rushed so much before getting approval. She asked if there was any tracking of unusual side effects. Her primary care doctor wanted her to get the second Covid 19 vaccine but her rheumatologist advised her not to get the second dose because of the high reaction she had. The delta variant of the covid 19 vaccine was high so she decided to get the second covid 19 vaccine. Patient visited emergency room and physician office. The patient underwent lab tests and procedures which included blood test: fine, electrocardiogram: fine, laboratory test: fine, magnetic resonance imaging head: fine, urine analysis: fine on 07Mar2021. The outcome of the events was reported as unknown.  The lot number for the vaccine, [BNT162B2], was not provided and will be requested during follow-up.