Chest pressure; heart pounding/ pounding while sedentary/Irregular heart rate; SKIPPED BEATS/ skipping while sedentary; This spontaneous case was reported by a consumer and describes the occurrence of PALPITATIONS (heart pounding/ pounding while sedentary/Irregular heart rate), EXTRASYSTOLES (SKIPPED BEATS/ skipping while sedentary) and CHEST DISCOMFORT (Chest pressure) in a 63-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 011J20A and 028L20a) for COVID-19 vaccination.     The patient's past medical history included Pericardial effusion on 29-Dec-2020, Heartbeats skipped (Last spring, patient noticed that during strenuous hikes, her heart, when pounding, would skip beats now and then. By fall, it was skipping beats every 2 to 5 beats.) in 2021, Urticaria and Hay fever. Previously administered products included for an unreported indication: SWINE FLU VACCINE in 1977. Past adverse reactions to the above products included Light headedness with SWINE FLU VACCINE. Concurrent medical conditions included Environmental allergy (Headaches, congestion), Allergy to chemicals (Nausea, vomiting, hives all over my body starting with where I had contact with the airline seats) since 17-Feb-2014, Drug allergy (Caused irregular heartbeat for a few hours about 12 hours after use/ Extreme heart arythmia) since 2007, Drug allergy (Allergy to Singulair, Disrupted sleep, increased stress/ psychological reaction), Food allergy (headaches, congestion.), Hypothyroidism since 2018, Asthma and Hypertension since 2006. Concomitant products included FEXOFENADINE from 2015 to an unknown date for Allergy, ZAFIRLUKAST from 2008 to an unknown date for Asthma, IBUPROFEN (ADVIL [IBUPROFEN]) for Headache, LISINOPRIL from 2015 to an unknown date for Hypertension, LEVOTHYROXINE from 2016 to an unknown date for Hypothyroidism.   On 05-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 02-Feb-2021 at 12:15 PM, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 10-Jan-2021, the patient experienced PALPITATIONS (heart pounding/ pounding while sedentary/Irregular heart rate) and EXTRASYSTOLES (SKIPPED BEATS/ skipping while sedentary). On 15-Jan-2021, the patient experienced CHEST DISCOMFORT (Chest pressure). On 29-Jan-2021, PALPITATIONS (heart pounding/ pounding while sedentary/Irregular heart rate), EXTRASYSTOLES (SKIPPED BEATS/ skipping while sedentary) and CHEST DISCOMFORT (Chest pressure) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 18-Dec-2020, Cardiac stress test: normal (normal) Good. On 18-Dec-2020, Echocardiogram: abnormal (abnormal) pre-vaccine echo showed some pericardial effusion.. On 29-Dec-2020, Computerised tomogram thorax: normal (normal) Heart appeared normal. On 26-Jan-2021, Pulmonary function test: normal (normal) normal to above normal. On an unknown date, Heart rate: abnormal (abnormal) Heart rate irregular. On an unknown date, SARS-CoV-2 antibody test: negative (Negative) Sars-Cov-2 Antibody IGA- negative, positive (Positive) Sars-Cov-2 Antibody IGG- positive. and negative (Negative) Sars-Cov-2 Antibody IGM- negative.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.       Patient stated that after the medications used for a month for pericarditis, pounding stopped, but not the pressure or skipping. Patient Wearing  a heart monitor for a month showed nothing of note (heart skipping an average of 2%). increase in Levothyroxine (75 MCG to 88 MCG) finally ended the heart skipping and chest pressure. No treatment medications were reported.   This case was linked to US-MODERNATX, INC.-MOD-2021-010524 (Linked Report).   Most recent FOLLOW-UP information incorporated above includes: On 25-May-2021: Follow up received, contains no new information On 13-Aug-2021: Follow up includes: updated consumer weight in KG's. added food allergy& updated description box for some of relevant history. added medical history: Hay fever, added lab tests:Sars-Cov-2 Antibody IGM, IGA, IGG and their results, added 2nd dose details and concomitant medications: Advil & updated start date for other concomitants, event causes the patient to visit doctor's office.; Sender's Comments:  US-MODERNATX, INC.-MOD-2021-010524: second dose case