I began to pass out and yelled for my husband, he said when he came in I was sitting on the toilet with my head back, eyes rolling back not responsive.; I had my 2nd vaccine at work early Sat the 9th and felt increasingly worse all day; I woke up at midnight and felt extreme malaise; I was covered in sweat; vomited; I checked my temp and it was 99.7°F; sore; I think I had either a seizure or a vasovagal response.; This is a spontaneous report from a contactable nurse (patient).   This 58-year-old female patient received the second dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE) (Lot  EJ1685 or FJ1685), intramuscular at single dose in the left arm on 09Jan2021 06:00 for Covid-19 immunisation. Medical history included atrial fibrillation on unknown date (1 episode), allergic to Keflex. There were no concomitant medications. The patient previously received the first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE) (Lot  EJ1685 or FJ1685), intramuscular in the left arm on 22Dec2020 for Covid-19 immunisation.  On 10Jan2021 01:00 AM, the patient experienced: I began to pass out and yelled for my husband, he said when he came in i was sitting on the toilet with my head back, eyes rolling back not responsive (loss of consciousness) (medically significant), I had my 2nd vaccine at work early sat the 9th and felt increasingly worse all day (feeling abnormal), Iwoke up at midnight and felt extreme malaise (malaise), I was covered in sweat (hyperhidrosis), vomited (vomiting), I checked my temp and it was 99.7°F (pyrexia), sore (pain), I think I had either a seizure or a vasovagal response (seizure). No treatment required. The outcome of the events was recovered.   The events were described as follows: I am healthy RN with no active medical problems. I had my 2nd vaccine at work early Sat the 9th and felt increasingly worse all day, I expected this so was not alarmed and went to bed around 10pm. I woke up at midnight and felt extreme malaise and went to the bathroom in case I might vomit, etc. and I tried to have a BM. I began to pass out and yelled for my husband, he said when he came in I was sitting on the toilet with my head back, eyes rolling back not responsive. He yelled at me for about 10 seconds and I came to, I was covered in sweat. I asked him to walk me back to the bedroom where I again passed out, fell to the floor and hit the bed, then was unresponsive again for about 10 seconds then came to again and vomited. After this I felt completely relieved of my malaise. I checked my temp and it was 99.7°F. After this I was sore but otherwise completely okay, the next day I had a temp of 99.5°F. Today I am back to normal. I think I had either a seizure or a vasovagal response. The vaccine was administered at Hospital Facility. The patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. The patient was not diagnosed with COVID-19 prior to vaccination. The patient had not been tested for COVID-19 since the vaccination. The patient was not pregnant at the time of vaccination.; Sender's Comments: Based on the close temporal relationship, the association between the event "began to pass out" with BNT162b2 can not 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.