in her heart, it was a very big tightness; felt tightness in her chest/Every time she took a breath when she was breathing in deeply it hurt; had shortness of breath on exertion; D-dimer test result was slightly raised at what she thinks was 16; She could not walk even around her house or she would get winded; having a pain in her chest when breathing; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient.  A 65 year-old female patient received bnt162b2 (BNT162B2), administered in arm left, administration date 19Aug2021 (Lot number: FD8448) at the age of 65 years as dose 1, single for covid-19 immunisation. Relevant medical history included: "Hashimoto's disease", start date: 1991 (ongoing); "Ulcerative colitis", start date: 2003 (ongoing); "Severe dairy allergy" (unspecified if ongoing), notes: Severe dairy allergy. Concomitant medication(s) included: SYNTHROID taken for autoimmune thyroiditis. Vaccination history included: Flu vaccine (She had trouble 4 years ago with a flu vaccine. Caller reported that she never went in and had a report on her symptoms, they went away. She had weakness in her legs and trouble walking after the flu vaccine.), administration date: 12Sep2017, when the patient was 61 years old, reaction(s): "weakness in her legs", "trouble walking". The following information was reported: CARDIAC DISORDER (non-serious) with onset 19Aug2021, outcome "recovered" (2021), described as "in her heart, it was a very big tightness"; CHEST DISCOMFORT (non-serious) with onset 19Aug2021, outcome "recovered" (2021), described as "felt tightness in her chest/Every time she took a breath when she was breathing in deeply it hurt"; CHEST PAIN (non-serious) with onset 2021, outcome "recovered" (2021), described as "having a pain in her chest when breathing"; DYSPNOEA EXERTIONAL (non-serious) with onset Aug2021, outcome "unknown", described as "had shortness of breath on exertion"; FIBRIN D DIMER INCREASED (non-serious) with onset Aug2021, outcome "unknown", described as "D-dimer test result was slightly raised at what she thinks was 16"; GAIT INABILITY (non-serious) with onset 2021, outcome "unknown", described as "She could not walk even around her house or she would get winded". Relevant laboratory tests and procedures are available in the appropriate section.  Additional information:  The patient was taking Synthroid for almost 30 years. Had different doses at different times of her life. Onset of Hashimoto's disease has been about 30 years ago. This autoimmune disease as well as her ulcerative colitis are part of the reason she did not get the Pfizer Covid-19 Vaccine right away. Onset of Ulcerative colitis maybe 18 years ago. This autoimmune disease as well as her Hashimoto's disease are part of the reason she did not get the Pfizer Covid-19 Vaccine right away. Regarding severe dairy allergy, She doesn't stop breathing but will have hives and want to throw up and diarrhea and everything. With that she can take Benadryl and she's ok. Trouble with strength of walking after regular flu vaccine, She has sensitivities to medication,trouble with regular flu vaccine 12Sep2017. Never got diagnosed with Guillain-Barre but was having trouble with strength of walking after that vaccine.Didn't go to doctor right away because busy and it resolved itself after couple of weeks-12 days. Doctor did not think she should take regular flu vaccines so she was concerned with Pfizer Covid-19 Vaccine.Regular flu vaccine:Brand name/Lot/NDC/Expiry:unknown,does not have product given at Rite aid. After she was administered the Pfizer Covid-19 Vaccine on 19Aug2021 she does not know if it was 4 or 5 hours later, but she had, in her heart, it was a very big tightness; so every time she took a breath when she was breathing in deeply it hurt. That lasted for about 45 minutes to 1 hour. They called a number that they said to call if you have any trouble and they sent them to the urgent care. The urgent care did an EKG on her and then he said it looked pretty normal, but he was pretty concerned so he sent her on to the hospital. She was admitted to the hospital the night of 19Aug2021 for these events and was discharged from the hospital around 04:30 or 05:00 the morning of 20Aug2021. While in the hospital they did the EKG and everything came out normal. They did a chest x-ray and then the only thing that did not come out normal was a D-dimer test. The D-dimer test result was slightly raised at what she thinks was 16. They went ahead and did a with contrast CT scan of her chest but she didn't have any problems that way. What continued on for the next 11-12 days was that she had shortness of breath with exertion. Normally she's been walking 1-2 miles a day at a fairly good pace. She could not walk even around her house or she would get winded. If she went out she couldn't even walk a block. She would have to come home and rest for about a half hour until her heart beat came down  which she never experienced before. Then after that she went to a Cardiologist and they did an echocardiogram which turned out fine. They did a stress test and that came out fine. The Cardiologist felt like she probably had a like an overreactive, or she does not know the word they used, but like an overreactive immune response to the Pfizer COvid-19 Vaccine; but that she probably would have that with Covid so he felt it was best to continue to take the second Pfizer Covid-19 Vaccine which she has scheduled for this Thursday.  She is just a little uncomfortable about getting the second Pfizer Covid-19 Vaccine. The Cardiologist has advised her to get the second dose of the Pfizer Covid-19 Vaccine, but caller's other doctor advised her not to get it. She called for information about these events relative to the Pfizer Covid-19 Vaccine and recommendations regarding dosing. The pain of breathing only lasted that first day of 19Aug2021, outcome otherwise unknown. There was still some tightness in her chest and there was the shortness of breath and that lasted another 11 days or 12 days. Outcome of other events unknown.  Follow-up attempts completed. No further information expected.