Felt like was going to pass out; Dizziness; Extended tachycardia; Moderna Covid-19 Vaccine First Dose: 25Feb2021/Second dose: 26Mar2021/Pfizer Cornavirus booster : 10Dec2021; Moderna Covid-19 Vaccine First Dose: 25Feb2021/Second dose: 26Mar2021/Pfizer Cornavirus booster : 10Dec2021; Booster; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 80 year-old female patient received bnt162b2 (BNT162B2), intramuscular, administered in deltoid left, administration date 10Dec2021 (Lot number: 33030BD) at the age of 80 years as dose 3 (booster), single for covid-19 immunisation. Relevant medical history included: "Had double mastectomy for cancer", start date: 2018, stop date: 2018; "cancer" (unspecified if ongoing). Concomitant medication(s) included: ANASTROZOLE; AMLODIPINE; HYDROCHLOROTHIAZIDE. Vaccination history included: Moderna covid-19 vaccine (First Dose: 25Feb2021, Lot: 010M20A, Exp: 19Jul2021 , Administered in left arm), administration date: 25Feb2021, when the patient was 79 years old, for Covid-19 immunisation, reaction(s): "The patient did not have AE following vaccination"; Moderna covid-19 vaccine (Second Dose: 26Mar2021, Lot: 010M20A, Exp: 19Jul2021, Administered in left arm), administration date: 26Mar2021, when the patient was 79 years old, for Covid-19 immunisation, reaction(s): "The patient did not have AE following vaccination". The following information was reported: OFF LABEL USE (non-serious), INTERCHANGE OF VACCINE PRODUCTS (non-serious) all with onset 10Dec2021, outcome "unknown" and all described as "Moderna Covid-19 Vaccine First Dose: 25Feb2021/Second dose: 26Mar2021/Pfizer Cornavirus booster : 10Dec2021"; IMMUNISATION (non-serious) with onset 10Dec2021, outcome "unknown", described as "Booster"; DIZZINESS (non-serious) with onset 15Dec2021, outcome "recovered" (15Dec2021), described as "Dizziness"; TACHYCARDIA (non-serious) with onset 15Dec2021, outcome "recovered" (15Dec2021), described as "Extended tachycardia"; PRESYNCOPE (non-serious) with onset 16Dec2021, outcome "unknown", described as "Felt like was going to pass out".  Additional Information: The patient stated that she had dizziness and tachycardia on 15Dec2021 and it lasted about 30min to an hour. She dismissed it, put out of head and relaxed, and looked to see what do for tachycardia.  About an hour before on 16Dec2021 she was in the grocery store and all of a sudden she got to the point where had to call for assistance, felt like was going to pass out. She was at the store and one of associates in store came to help. The associate assisted to a place to sit, asked if she had eaten. The associate got her some Pita chips and water. The patient sat, ate chips, drank water, went to restroom, then went to register for purchases and went to car. After she left the grocery store she was going to go to Emergency, but home was closer. The patient did not visit emergency room and not visit physician office for adverse event.There was no history of all previous immunization with the Pfizer vaccine considered as suspect. There was no additional vaccines administered on same date of the Pfizer suspect. The patient did not have prior vaccination within 4 weeks.