My heart rate will jump up to the 120s just standing and doing normal none strenuous activities; my heart rate will go up beyond 150s/ rarely go over 130; feel light headed and dizzy; Major brain fog; heart palpitations; chronic fatigue/ exhausted; orthostatic intolerance; POTs; This is a spontaneous report from a non-contactable nurse (patient) reported for herself. A 26-years-old female patient (patient was not pregnant at the time of vaccination) received second dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, Solution for injection, Lot number: EN6201, Expiration date: unknown) intramuscular, administered in left arm on 12Feb2021 at 09:00 am (age at vaccination was 26 years) as dose 2, single for COVID-19 immunization. The patient's medical history included fatigue (probably had chronic fatigue, but undiagnosed). The patient did not have any known allergies. The patient did not receive any concomitant medications or other medications within 2 weeks of vaccination. The patient previously received first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, Solution for injection, Lot number: EK9231, Expiration date: unknown) intramuscular, administered in left arm on 21Jan2021 at 09:00 am (age at vaccination was 26 years) as dose 1, single for COVID-19 immunization and experienced fatigued. The facility where the most recent COVID-19 vaccine was administered was Hospital. The patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. Prior to vaccination, the patient was not diagnosed with COVID-19. Since the vaccination, the patient has not been tested for COVID-19. On 26Feb2021 at 08:00, the patient's heart rate would jump up to the 120s just standing and doing normal nonstrenuous activities, her heart rate would go up beyond 150s/ rarely go over 130, felt lightheaded and dizzy, major brain fog, heart palpitations, chronic fatigue/exhausted, orthostatic intolerance and POTs (Postural orthostatic tachycardia syndrome). About 2 weeks after receiving her 2nd dose, she began to feel lightheaded and dizzy. Major brain fog and heart palpitations. Recently in the last couple months she has been diagnosed with chronic fatigue. She had probably had that since being a teenager and it had come and gone. But after receiving her vaccines she had become fatigued again but had developed these new symptoms as stated above. Her heart rate would jump up to the 120s just standing and doing normal nonstrenuous activities (like doing laundry) her heart rate would go up beyond 150s. She had a Holter monitor to evaluate what was going on, she also had her smart watch monitoring her heart rate during the day. Her doctor diagnosed her with chronic fatigue along with orthostatic intolerance or POTs. She thought she was getting a little better with her new meds, but some days she reverted back to waking up exhausted and her heart rate was still not under 100 bpm, but she rarely went over 130 now and didn't have palpitations or felt dizzy or lightheaded. The adverse events resulted in Doctor or other healthcare professional office/clinic visit. The patient underwent lab tests which included heart rate: 120, heart rate: 150, heart rate: 130, holter monitor: results not reported on an unspecified date in 2021. Therapeutic measures were taken as a result of the events. The events were reported as non-serious. The outcome of the events feel light headed and dizzy and heart palpitations was resolved on an unspecified date of 2021. The outcome of all the other events was not resolved.  No follow-up attempts are possible. No further information is expected.; Sender's Comments: Based on the information provided in the narrative, a causal association between the suspect drug and increase in heart rate cannot be completely 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.