booster reaction (immunisation reaction); Heart rhythm going into atrial fibrillation; Unspecified reaction to COVID; This is a solicited report received from contactable reporter(s) (Consumer or other non HCP). The reporter is the patient. Other Case identifier(s): UNT-2022-012548, UNT-2022-024775.  A 62-year-old female patient received BNT162b2 (BNT162B2), as dose number unknown (booster), single (Batch/Lot number: unknown) at the age of 62 years for covid-19 immunisation; treprostinil sodium (TYVASO), first regimen since 27Jan2022 (Batch/Lot number: unknown) at 0.6 mg/ml and second regimen since 2022 (Lot number: 2102227, Expiration Date: 30Nov2023) at 4x/day (54 ug, 4x/day (current dose was reported as up to 54 ug (up to 9 breaths), four times a day)), all respiratory inhalation for pulmonary arterial hypertension. The patient's relevant medical history included: "Pulmonary arterial hypertension" (ongoing). Concomitant medication(s) included: OPSUMIT. Vaccination history included: Covid-19 vaccine (Primary Immunization series complete but unknown manufacturer.), for COVID-19 immunization, reaction(s): "COVID-19". The following information was reported: IMMUNISATION REACTION (non-serious) with onset 18May2022, outcome "unknown", described as "Unspecified reaction to COVID"; IMMUNISATION REACTION (hospitalization, medically significant) with onset 2022, outcome "unknown", described as "booster reaction (immunisation reaction)"; ATRIAL FIBRILLATION (hospitalization, medically significant) with onset 25Sep2022, outcome "unknown", described as "Heart rhythm going into atrial fibrillation". The patient was hospitalized for atrial fibrillation (start date: 25Sep2022, discharge date: 26Sep2022, hospitalization duration: 1 day(s)); for immunisation reaction (start date: 2022, discharge date: 2022). The event "unspecified reaction to covid" required emergency room visit. The patient underwent the following laboratory tests and procedures: Weight: (2022) 153 lbs. The action taken for treprostinil sodium was unknown. Clinical information: The patient began therapy with IH Tyvaso (treprostinil sodium, concentration of 0.6 mg/ml) delivered by Tyvaso Inhalation Device (TD-300/A), on 27Jan2022 for secondary pulmonary arterial hypertension. On 18May2022, 3 months, and 22 days after initiating Tyvaso, the patient was seen in the emergency department regarding an unspecified reaction to COVID [coronavirus disease] vaccine (immunisation reaction) and was released. On 25Sep2022, 7 months, and 30 days after initiating Tyvaso, the patient was hospitalized due to heart rhythm going into atrial fibrillation (atrial fibrillation, hospitalized and medically significant). She was discharged on 26Sep2022. On an unreported date in 2022, the patient was hospitalized for one night for COVID [coronavirus disease] booster reaction (immunisation reaction) and was released on an unreported date in 2022. She was using Tyvaso.  The reporter's assessment of the causal relationship of "heart rhythm going into atrial fibrillation" and "booster reaction (immunisation reaction)" with the suspect product(s) BNT162b2 was not provided at the time of this report. Since no determination has been received, the case is managed based on the company causality assessment. The reporter considered "unspecified reaction to covid" related to BNT162b2.  The reporter did not provide causality for the event of immunisation reaction with Tyvaso.  Case Comment/Senders Comment: The company has assessed the serious adverse events of atrial fibrillation and immunisation reaction as not related to IH Treprostinil and TD300/A device. Remodeling of the right ventricle and the right atrium appears to generate the underlying arrhythmogenic substrate in patients with pulmonary hypertension which likely caused the event of atrial fibrillation. Immunisation reaction was likely due to complications from administration of COVID-19 vaccine.  Follow-up (27Oct2022): This is a solicited follow-up report from a Non-Interventional Study (MARKETING PROGRAM NAME NOT AVAILABLE) based on information received by Pfizer, MFR Control No. UNT-2022-024775). Updated information includes: Verbatim of Historical vaccine updated to COVID. Lab data added. Start date added, lot number, expiration date of dosage regimen slider#02 of co-suspect Tyvaso updated. Events Atrial fibrillation and Immunisation reaction with onset dates were added. Hospitalization start date and stop date were added for the events.  No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected.; Sender's Comments: Based on available information, a possible contributory role of Comirnaty vaccine cannot be excluded for the reported events of "heart rhythm going into atrial fibrillation" and "booster reaction (immunisation reaction)" . The impact of this report on the benefit/risk profile of the Pfizer drug 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.