Myocardial infarction /heart attack; Dose number in series 1-Janssen COVID-19 Vaccine; Dose number in series 2-Moderna mRNA-1273 Vaccine; This spontaneous case was reported by a consumer and describes the occurrence of MYOCARDIAL INFARCTION (Myocardial infarction /heart attack) in a male patient of an unknown age who received COVID-19 VACCINE NRVV AD26 (JNJ 78436735) (JANSSEN COVID-19 VACCINE) for an unknown indication. The occurrence of additional non-serious events is detailed below.    Co-suspect product included mRNA-1273 (Moderna COVID-19 Vaccine) for Prophylactic vaccination.    No Medical History information was reported.   On 17-Dec-2021, the patient received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient started COVID-19 VACCINE NRVV AD26 (JNJ 78436735) (JANSSEN COVID-19 VACCINE) (unknown route) 1 dosage form. On 17-Dec-2021,  after starting COVID-19 VACCINE NRVV AD26 (JNJ 78436735) (JANSSEN COVID-19 VACCINE), the patient experienced INTERCHANGE OF VACCINE PRODUCTS (Dose number in series 1-Janssen COVID-19 Vaccine; Dose number in series 2-Moderna mRNA-1273 Vaccine). On 18-Dec-2021, the patient experienced MYOCARDIAL INFARCTION (Myocardial infarction /heart attack) (seriousness criteria death and medically significant). The patient died on 18-Dec-2021. The reported cause of death was Heart attack. It is unknown if an autopsy was performed. At the time of death, INTERCHANGE OF VACCINE PRODUCTS (Dose number in series 1-Janssen COVID-19 Vaccine; Dose number in series 2-Moderna mRNA-1273 Vaccine) had resolved. Not Provided          Concomitant product use was not provided by the reporter.  Treatment information was not provided.  Company Comment: This is a spontaneous case of interchange of vaccine products for this male patient, of unknown age, with history of co-suspect administration of a dose of the Janssen COVID-19 vaccine, who experienced the unexpected, serious (fatal and medically significant) AESI of myocardial infarction. The event occurred 1 day after administration of an unspecified dose of the Moderna mRNA-1273 vaccine. On 18Dec2021, the patient experienced a heart attack and died. No further details were provided. It is unknown if an autopsy was performed. The history of co-suspect administration of the Janssen COVID-19 vaccine remains a confounder. The benefit-risk relationship of the Moderna mRNA-1273 vaccine is not affected by this report.   Reporter did not allow further contact; Sender's Comments: This is a spontaneous case of interchange of vaccine products for this male patient, of unknown age, with history of co-suspect administration of a dose of the Janssen COVID-19 vaccine, who experienced the unexpected, serious (fatal and medically significant) AESI of myocardial infarction. The event occurred 1 day after administration of an unspecified dose of the Moderna mRNA-1273 vaccine. On 18Dec2021, the patient experienced a heart attack and died. No further details were provided. It is unknown if an autopsy was performed. The history of co-suspect administration of the Janssen COVID-19 vaccine remains a confounder. The benefit-risk relationship of the Moderna mRNA-1273 vaccine is not affected by this report.; Reported Cause(s) of Death: Heart Attack