heart failure occurred after receiving vaccines; got 2 doses of the Moderna Covid-19 Vaccine, then got myocarditis; got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine; got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine; This spontaneous case was reported by a patient and describes the occurrence of CARDIAC FAILURE (heart failure occurred after receiving vaccines) and MYOCARDITIS (got 2 doses of the Moderna Covid-19 Vaccine, then got myocarditis) in a 36-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 040B21A and 038A21A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     Patient had no prior heart issues. Patient was perfectly healthy.    On 27-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 24-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 24-Nov-2021, the patient experienced COVID-19 IMMUNISATION (got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine) and INTERCHANGE OF VACCINE PRODUCTS (got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine). On an unknown date, the patient experienced CARDIAC FAILURE (heart failure occurred after receiving vaccines) (seriousness criterion medically significant) and MYOCARDITIS (got 2 doses of the Moderna Covid-19 Vaccine, then got myocarditis) (seriousness criterion medically significant). At the time of the report, CARDIAC FAILURE (heart failure occurred after receiving vaccines) had not resolved and MYOCARDITIS (got 2 doses of the Moderna Covid-19 Vaccine, then got myocarditis), COVID-19 IMMUNISATION (got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine) and INTERCHANGE OF VACCINE PRODUCTS (got 2 doses of the Moderna Covid-19 Vaccine/received one booster dose of Pfizer Covid-19 vaccine) outcome was unknown.            No concomitant medications were provided by the reporter.  Patient got 2 doses of the Moderna Covid-19 Vaccine, then got myocarditis  It was reported that patient heart was barely functioning now and would get a pacemaker.  Patient received one booster dose of Pfizer Covid-19 vaccine with batch number as FH8030 on 24-Nov-2021.  No treatment medications were provided by the reporter.  Company Comment:  This is a spontaneous  case concerning a 36-year-old, female patient previously healthy, who experienced the unexpected serious (medically significant) AESI of cardiac failure and expected serious (medically significant) AESI of myocarditis. The events occurred after the administration of the second dose of mRNA-1273 vaccine, however start dates were not reported and latency could not be estimate with the information provided. Patient will required a pacemaker but no further information on clinical course, investigations and treatment received was available in the report. A third dose was administered with Pfizer vaccine 7 months after the second mRNA-1273 dose.  Revaccination with different COVID-19 vaccine and Interchange of vaccine products is noted in this case.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 15-Nov-2022: Live Follow-up received contains event Heart failure added, vaccination details and narrative updated.; Sender's Comments: This is a spontaneous  case concerning a 36-year-old, female patient previously healthy, who experienced the unexpected serious (medically significant) AESI of cardiac failure and expected serious (medically significant) AESI of myocarditis. The events occurred after the administration of the second dose of mRNA-1273 vaccine, however start dates were not reported and latency could not be estimate with the information provided. Patient will required a pacemaker but no further information on clinical course, investigations and treatment received was available in the report. A third dose was administered with Pfizer vaccine 7 months after the second mRNA-1273 dose.  Revaccination with different COVID-19 vaccine and Interchange of vaccine products is noted in this case.  The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.