Heart Palpitations; Sinus tachycardia; high blood pressure; fever; woke up in a pool of sweat; headache; ringing in her ears; Potassium was a little low, it was 3; This is a spontaneous report from a contactable nurse (patient).  A 35-year-old female patient received second single dose of BNT162B2 (Pfizer-BioNTech Covid-19 vaccine, lot number EK9231, expiration date Apr2021) intramuscularly on 12Jan2021 (between 8:30 to 9 am) at left deltoid for Covid-19 prevention. The first dose was received on Wednesday (unspecified date). Patient had no medical history and had no concomitant medications. At night of 12Jan2021, the patient had a fever of 102, but she went to bed with it and she woke up in the morning around 4:30 or 5 am (13Jan2021) in a pool of sweat, so she took her temperature and she was fever with 103.6. Patient took Motrin (Store Brand, lot number as either: 0GE2417A or OGE2417A, expiry: Apr2022) three 200 mg tablets, for a totally of 600 mg for the fever and had a cold shower, and the temperature came down to 103. Then after like 10-15 minutes of her laying on the couch with ice packs on her arms and stuff, it went down to 102.6. Patient was not going to go to the ER for just the fever, but then she started having heart palpitations, and she took her blood pressure and it was 170/113 and her heart rate was 176. Patient went to the hospital, and when they took her heart rate, it was 156. She had her blood taken at the hospital and everything was normal, except that her Potassium was a little low, it was 3. The ER did an EKG that showed Sinus Tachycardia and she was given IV Fluids (two boluses of 0.9% Normal Saline, 2000 mL total via IV, a bag of Potassium IV, two oral tablets of Potassium, unspecified total dose), and everything went back down. She had to call out from work that day and planed to follow up with her Primary Care Physician (PCP) in a couple of days. Patient was no longer had the fever, high blood pressure or high heart rate, as when she left the ER this morning, her temperature was 98, blood pressure was 111/82, and her heart rate was 96. She felt good now, but she did not know if it could happen again. Patient thought that it was maybe just her immune response to the vaccine, so she would say that she has recovered probably close to completely. Patient also had a headache and ringing in her ears, and those had resolved by now as well. The events Fever, Sinus tachycardia, Heart Palpitations, high blood pressure resolved on 13Jan2021 and other event resolved in Jan2021. The patient stated that the events (Fever, Sinus tachycardia, Heart Palpitations, high blood pressure) could have been serious with her blood pressure being so high, but it was not so serious because she did the right thing and went to the ER for treatment and got fluids. She believes the events (Fever, Sinus tachycardia, Heart Palpitations, high blood pressure) are medically significant. The patient believes that the events she experienced were directly caused by her receiving the vaccine, as she has never had these symptoms before other than she of course has had fevers in her life in the past.; Sender's Comments: A possible contribution role of BNT162B2 (Pfizer-BioNTech Covid-19 vaccine) to the onset of the reported events cannot be 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.