This is a spontaneous report from a contactable nurse (patient). A 68-year-old female patient received first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, Formulation: Solution for injection, Lot # EN6201), via intramuscular (IM) injection left deltoid on 13Feb2021 08:40 as single dose for covid-19 immunisation. Medical history included respiratory issues. Concomitant medications were not reported. The patient experienced her heart rate started increase/tachycardia on 13Feb2021, she felt her heart pounding and she felt very ill on an unknown date in Feb2021. The report received as, caller states that she had her first COVID vaccine at about 8:40 AM on Saturday morning 13Feb2021. Caller started a guided meditation at 2 pm that day and at 2:05 pm, the caller became aware of her heartbeat. Caller states that her watch told her that her heartbeat was in the 90s, and after a bit it went into the 100s and then 110s, then 120s then 130s then 140s and by 4pm, the caller's heartbeat was in the 160s and the highest she calculated was 168. Caller states that when her heartrate was in the 150s and 160s, she was feeling like her heart was pounding in her chest like it was going to break through, and she felt very ill. She felt badly. Caller states that she called her friend to come over and take her to the ER, but her friend ended up leaving about 6pm because the caller's heartrate was back down to about 145. Caller did not end up going to the ER. Caller states that as the evening progressed, her heartrate ranged from the 90s to the 100s (103, 104). Yesterday it was back to normal and her heartrate was back in the 70s all day and she felt fine. Caller states that she had tried deep breathing and relaxation techniques and nothing worked to bring her heart rate down. Normally, if she gets stressed she deep breathes. She contacted her primary care provider by email and they sent the chart to allergist to help and said if her heart rate went above 110 to go to the emergency room. The caller asked if she should receive her second dose. Caller states that she was scared during the event, so she did contact (Health care company name), and they told the caller that she should have gone to the hospital. Caller states that (Health care company name) told the caller that the caller may not get the tachycardia from the second dose, but that the caller needs to let the nurses know about her side effect to the first dose. Caller was also informed by (Health care company name) that if the caller's heartrate goes above 110, the caller should go the ER. Patient weight provides as her weight as between 120 and 121 pounds. Event details was provided as, caller states that she did try to call Pfizer on Sunday and she left a message, but no one got back to her, and she wanted to ensure this was reported. Caller states that by Sunday she was fine. Caller started having tachycardia Saturday afternoon and it lasted into the evening. Caller states that by Sunday evening she was running in the 90s-100s but staying under 105, but she woke up fine on Sunday. Seriousness was reported as, caller states that it was very serious, and she should have gone to the ER but she didn't. Suspect Product and Indication details was provided as, caller reports that she got the product for COVID Prevention and because she has respiratory issues, but no further details were provided by the caller. Caller confirms that she received no other vaccines on the same day as the COVID vaccine. Concomitant Medications, History and Investigations was reported as, caller states no to these questions. Caller states that in fact, she just had millions of lab tests and everything was fine and being that she was relaxing in a meditation when it started, caller is sure it was from the vaccine. Caller states that she tried deep breathing and relaxation techniques and this tachycardia was happening, and she could not control it. The patient underwent lab tests and procedures which included on 13Feb2021, heart rate was 160 seconds, increase throughout the day /heartbeat was in the 90s, and after a bit it went into the 100s and then 110s, then 120s then 130s then 140s, 168 seconds, highest she calculated, 145 seconds at 6:00 PM the average was down /heartrate ranged from the 90s to the 100s, on 15Feb 2021, heart rate was 70 seconds on 15Feb2021 heartrate was back /all day and she felt fine, pulse: ranged from 90 to lower 100s (103, 104) on 13Feb2021 (as the evening progressed), and normal on 15Feb2021, lab test: fine on an unknown date. The outcome of the event Her heart rate started to increase/Tachycardia was recovered on 14Feb2021 and remaining events was unknown.; Sender's Comments: As there is limited information in the case provided, the causal association between the event her heart rate started increase/tachycardia and the usage of the vaccine BNT162B2 cannot be excluded because of temporal association. The case will be reassessed once new information is available.  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.