My chest started hurting a lot; Heart failure; sick; arm still hurts at the injection site; This spontaneous case was reported by a consumer and describes the occurrence of CHEST PAIN (My chest started hurting a lot) and CARDIAC FAILURE (Heart failure) in a 41-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 10-Sep-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 10-Sep-2021, the patient experienced CHEST PAIN (My chest started hurting a lot) (seriousness criterion hospitalization). On an unknown date, the patient experienced CARDIAC FAILURE (Heart failure) (seriousness criterion medically significant), ILLNESS (sick) and VACCINATION SITE PAIN (arm still hurts at the injection site). The patient was hospitalized for 4 days until 15-Sep-2021 due to CHEST PAIN. At the time of the report, CHEST PAIN (My chest started hurting a lot), CARDIAC FAILURE (Heart failure) and ILLNESS (sick) outcome was unknown and VACCINATION SITE PAIN (arm still hurts at the injection site) had not resolved.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.       No relevant concomitant medications were reported. After getting discharged from hospital on 15 Sep 2021, patient went back to hospital and was kept there for three weeks and on 25 Oct 2021, was discharged form hospital. She again went back to hospital and was kept there for 2.5 weeks and was discharged on 26 Nov 2021. She went to six different doctors and was told that it's from the COVID shot. Different kind of tests were performed with no results provided.  No treatment information was provided.  Company comment: This spontaneous case concerns a 41-year-old female patient with no  medical history reported, who experienced the unexpected serious (hospitalization) event of Chest pain and the unexpected serious (medically significant) event/AESI of Cardiac failure after mRNA- 1273 vaccine. The onset of the event Chest pain occurred on the day after the first dose of mRNA- 1273 vaccine and led to hospitalization. Cardiac failure was diagnosed on an unknown date after the first dose. The patient was initially admitted for 4 days, and later readmitted on two occasions for 3 weeks and 2.5 weeks. She was discharged 2 months and 16 days after the first dose. Very limited information is available regarding hospitalization, diagnostic work-up and treatment provided.  The benefit-risk relationship of mRNA- 1273 vaccine is not affected by this report.; Sender's Comments: This spontaneous case concerns a 41-year-old female patient with no  medical history reported, who experienced the unexpected serious (hospitalization) event of Chest pain and the unexpected serious (medically significant) event/AESI of Cardiac failure after mRNA- 1273 vaccine. The onset of the event Chest pain occurred on the day after the first dose of mRNA- 1273 vaccine and led to hospitalization. Cardiac failure was diagnosed on an unknown date after the first dose. The patient was initially admitted for 4 days, and later readmitted on two occasions for 3 weeks and 2.5 weeks. She was discharged 2 months and 16 days after the first dose. Very limited information is available regarding hospitalization, diagnostic work-up and treatment provided.  The benefit-risk relationship of mRNA- 1273 vaccine is not affected by this report.