tachycardia; chest felt heavy; This is a spontaneous report from a contactable Physician via Medical Information Team.   A 51-years-old female physician (patient) reported for herself and received BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, formulation: Solution for injection, Lot Number: EN6204, Expiry date and NDC number were unknown) via intramuscular route in right arm on 11Mar2021 at 18:15 (at the age of 51-years-old) as dose 1, single for Covid-19 immunisation. The patient medical history included sinus tachycardia From Unspecified date to ongoing, had for years and she had COVID-19 on unknown date in Jul2021. The patient concomitant drugs included ongoing Bisoprolol (MANUFACTURER UNKNOWN, has taken for years, strength 5mg tablets), she takes 2.5 mg daily for Sinus tachycardia and immune support vitamins (MANUFACTURER UNKNOWN) from unspecified date for unknown indication. The patient did not have history of any previous allergies to specific products or any conditions indicative of an allergy. The patient called about the COVID 19 vaccine. She received her first dose of the COVID-19 vaccine on 11Mar2021 at a local (pharmacy name), She didn't realize she had had an allergic reaction classified as severe until the (pharmacy name) sent her a questionnaire regarding her upcoming second COVID-19 vaccine. About 24 hours after she received the COVID-19 vaccine she experienced tachycardia at 145bpm on 12Mar2021 at 18:00, she has a Fitbit watch, so she was able to see her heartrate, while probing for specific event details she reports her Fitbit watch was vibrating with her heartrate and her chest felt heavy (on 12Mar2021). She doubled the dose of her medication and while she was sleeping her heartrate was around 105-109 beats per minute. She kept her Fitbit watch on at night and monitored her heartrate throughout the night. With rest her heartrate returned to a normal range, she doubled her dose of her regular medication to override that extreme heart rate, she wanted to know what was being recommended on getting the second COVID-19 vaccine. She was on the fence about getting that second COVID-19 vaccine, but she knows the benefits of getting it, she doesn't know what other side effects getting the second COVID-19 vaccine may cause. The tachycardia started around 6:00PM on 12Mar2021, around dinner time. Her heartrate went up quickly, like she was just sitting, and her heartrate ramped up instantly. She immediately took her medication and her heartrate started coming down. She has a portable EKG machine at her house, and it showed sinus tachycardia, nothing else going on, she also has a blood pressure cuff to check her blood pressure and heart rhythm, she states if you label yourself as having a severe reaction you will be unable to get the second COVID-19 vaccine. The tachycardia was listed under severe reactions. The patient did not visit emergency room, physician office, intensive care unit, did not require medical intervention, was not hospitalized. The patient did not receive Vaccine at Military Facility, had no history of all previous immunization with the Pfizer vaccine considered as suspect. Laboratory details included heart rate at 145 bpm and went up quickly on 12Mar2021. The patient did not take Prior Vaccinations (within 4 weeks) or had AE(s) following prior vaccinations, did not receive any recent vaccines for any other conditions prior to the event being reported. The outcome of the events was resolved on 13Mar2021.  Relatedness of drug to reaction(s)/event(s): Reaction assessed: tachycardia, Source of assessment: Primary Source Reporter, Method of assessment: Global Introspection. Drug result: Related. Relatedness of drug to reaction(s)/event(s): Reaction assessed: chest felt heavy, Source of assessment: Primary Source Reporter, Method of assessment: Global Introspection, Drug result: Related. Verbatim event relatedness: COVID-19 Vaccine: tachycardia-Related, COVID-19 Vaccine: chest felt heavy-Related.