CARDIAC CHEST PAIN; This approximately 42 -year-old, Male subject was participating in a Study and experienced the medically significant serious adverse event of special interest of cardiac chest pain.  The subject's medical history, as provided by the investigator, included dislocated left knee, environmental allergies, torn cartilage right shoulder, lactose intolerant, vasectomy, left eye amblyopia, allergy to cat and dog dander, allergy to walnuts, asthma, eczema - bilateral upper arms, nephrolithiasis right side, Lyme disease, left knee arthroscopic surgery, and right shoulder arthroscopic surgery. Concomitant medications included salbutamol, tilactase, ibuprofen, prednisone, sertraline, colecalciferol, fish oil, and ascorbic acid.  The subject was randomized to receive blinded intramuscular mRNA-1273 for SARS-CoV-2 vaccination and was unblinded on 12 Feb 2021. The subject received the first dose of mRNA-1273 on 14 Sep 2020, the second dose on 12 Oct 2020, and a booster dose on 12 Oct 2021. The subject's last dose of mRNA-1273 prior to event onset was on 12 Oct 2021.  On 13 Oct 2021, the subject experienced cardiac chest pain. The subject reported developing a low-grade fever, myalgias, and chest pain that awoke him from sleep around midnight. The chest pain was described as sharp, constant, non-exertional, and worse when lying down on his left side. He denied shortness of breath or dyspnea on exertion. It was noted that the subject had no history of coronary artery disease.  On 14 Oct 2021, the pain got worse and the subject went to the emergency room. He was admitted to the hospital on the same day. His troponin was elevated. An echocardiogram and coronary catheterization were performed, both reported as unremarkable without significant coronary artery disease. After being treated with carvedilol, troponin levels came down.   On 17 Oct 2021, the subject was discharged from the hospital. The subject reported feeling better with minimal mild, intermittent chest pressure. The subject reported a diagnosis of non-ST elevation myocardial infarction and denied being diagnosed with myocarditis or pericarditis. The subject was scheduled to follow-up with his primary care provider and cardiology. A cardiac magnetic resonance imaging scan was scheduled for the end of November.  Action taken with study drug in response to the event was not applicable, as the subject had already received all scheduled doses.  The event, cardiac chest pain, was reported as resolving with sequelae (still had aches from time to time; subject stated he felt pain when exercising).   The investigator assessed the event, cardiac chest pain, as related to study drug (per the investigator, as symptoms started the day after receiving the booster dose) and not related to study procedure.   Follow-up received on 26 Oct 2021 and 02 Nov 2021 included updated event outcome, event term (previously chest pain), and concomitant medication details.   On 26 Oct 2021, the safety database was searched for events similar to Chest Pain using the following search criteria: PT: Chest pain cardiac, Myocarditis and Troponin increased.  1257 cases were retrieved from PM and CT settings, excluding the index case; out of 1257, one was a CT case.  1208 cases were retrieved with PT: Myocarditis and 48 cases were retrieved with PT: Troponin increased.  The CT case (MOD-2021-273925) reported an event with PT: Troponin increased.  As of 26 Oct 2021, for mRNA-1273, 2 similar events were retrieved, including the current index case.  One case reporting event Troponin increased was previously submitted as Safety Reports (MOD-2021-273925).  There were 0 of subtotal cases unrelated cases were non- Safety Reports (expected and related or unexpected and unrelated or expected and unrelated to the IMP) reporting the following events: Chest pain cardiac (0), Myocarditis (0), Troponin increased (0).  The case previously reported as (MOD-2021-273925) concerns a 70-year-old, female subject with relevant medical history of dyslipidemia, hypertension, type II diabetes, cardiac stress test positive about 20 years ago, overweight and sinus bradycardia who experienced dizziness and elevated troponin. The events occurred 29 days after receiving single booster shot dose of mRNA-1273.211. At the time of the events ECG revealed known sinus bradycardia and echocardiogram revealed borderline concentric left ventricular hypertrophy. Both events resolved within two days. The event elevated troponin was assessed as related to mRNA-1273.211 in agreement with the Investigator. The event dizziness was assessed as unrelated to mRNA-1273.211 in agreement with the Investigator.  The index case concerns a 42 -year-old, male subject with a medical history relevant for asthma and Lyme disease, and NO history of CAD. Other medical history included dislocated left knee, environmental allergies, torn cartilage right shoulder, lactose intolerance, vasectomy, left eye amblyopia, eczema, and nephrolithiasis. The subject experienced chest pain on the day following the booster dose; the subject had received the first dose of mRNA-1273 1 year 1 month prior to the event and the second dose, 1 year prior to the event. The event chest pain developed in the context low-grade fever and myalgia. The chest pain was sharp, constant, non-exertional, and worsened lying down on the left side. The subject went to the ER and his troponin was noted to be elevated, echocardiogram and coronary catheterization were unremarkable. The subject was treated with carvedilol, and his troponin levels decreased. A final diagnosis was not provided but per the subject's recollection it was NSTEMI versus myocarditis or pericarditis; medical records are pending. The outcome of the event chest pain was unknown. The event was considered related to the study vaccine in agreement with the Investigator based on close temporal association.  In the index case the chest pain happened one day following the booster injection, which favors causal association. There was no history of CAD and no SOB, and the subject had accompanying symptoms of fever and myalgia. No final diagnosis was provided but differential diagnoses included NSTEMI vs myocarditis/pericarditis. In all 3 conditions, troponin could be elevated, accompanying symptoms of fever and myalgia as well as subject's age and lack of history of CAD with unremarkable coronary catheterization, are more in favor of possible myocarditis/pericarditis. Final diagnosis is to be confirmed once medical records are received.  Based on review of available data, and temporal association, the Sponsor cannot rule out a possible cause and effect relationship between administration of mRNA-1273 and the occurrence of Chest pain.  After review of the clinical details and investigator comments pertaining to this adverse event, and based upon experience to date, the Sponsor does not believe that changes to the conduct of this clinical trial are warranted. The Company will continue to monitor these and other serious adverse events reported in association with the RA and will communicate any relevant changes to the protocol, Informed Consent Form, Investigator's Brochure, and/or Core Safety Information.; Reporter's Comments: This case concerns a 42 -year-old, male subject with a medical history of dislocated left knee, environmental allergies, torn cartilage right shoulder, lactose intolerant, vasectomy, left eye amblyopia, allergy to cat and dog dander, allergy to walnuts, asthma, eczema - bilateral upper arms, nephrolithiasis right side, Lyme disease, left knee arthroscopic surgery, and right shoulder arthroscopic surgery who experienced the unexpected event of special interest of cardiac chest pain. The event occurred 1 year 1 month after the first dose of mRNA-1273, 1 year after the second dose and the following day of the booster dose. The subject reported a diagnosis of non-ST elevation myocardial infarction and denied being diagnosed with myocarditis or pericarditis. Action taken with study drug in response to the event, dechallenge and rechallenge were not applicable as the subject had already received all scheduled doses. The outcome of the event chest pain was reported as resolving with sequelae . The event was considered related to the study vaccine in agreement with the Investigator based on close temporal association.  Additional information, including final diagnosis ,has been requested.