sudden cardiac arrest; This spontaneous case was reported by an other health care professional and describes the occurrence of CARDIAC ARREST (sudden cardiac arrest) in a 16-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) for COVID-19 prophylaxis.     No Medical History information was reported.    On an unknown date, the patient received dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) 1 dosage form. On 24-Feb-2023, the patient experienced CARDIAC ARREST (sudden cardiac arrest) (seriousness criteria hospitalization, medically significant and life threatening). The patient was hospitalized from 24-Feb-2023 to 02-Mar-2023 due to CARDIAC ARREST. At the time of the report, CARDIAC ARREST (sudden cardiac arrest) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Laboratory test: revealed no abnormalities..     For mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (Unknown), the reporter considered CARDIAC ARREST (sudden cardiac arrest) to be related.    Concomitant medications were not reported.  Patient was 100% healthy, no pre-exiting conditions, no symptoms, no waning. On 24 Feb 2023, 16 year old patient had collapsed at school. Patient was unresponsive and being rushed to the hospital in an ambulance. Patient had gone into sudden cardiac arrest. School nurse grabbed and AED. Using 4 rounds of CPR and one shock form the AED and was able to resuscitate patient twice before paramedics arrived. When patient began to wake up at the hospital patient was confused and agitated. Reporter was not sure if patient had suffered brain damage or would have any other complications from the oxygen deprivation. The doctors and nurses were having difficulties getting him to cooperate so they could treat him.  Still had not made it to the hospital yet and every video update reporter received seem worse and worse. Finally, patient's mother arrived and the moment patient heard mother's voice, patient responded and all vitals began to calm instantly. That was the first moment patient's mother began to feel a glimmer of hope that patient was still there. The emergency room was able to stabilize patient and ran some tests but could not find any signs of diseases or obvious risk factors. During the ambulance ride to the next hospital patient regained full consciousness. Patient had no memory of anything that happened, but he passed All of his cognitive tests. The next day began a battery of every test you can think of. He had a huge team of cardiologists, and incredible nurses and aided. Test after test revealed no abnormalities. Patient basically moved into the hospital. After 5 days of rigorous testing and absolutely no answers the decision was made to implant an ICD. After 3 hours in surgery patient came out smiling. Patient now had a subcutaneous ICD that will deliver a life-saving shock in the event of another arrest. This device was the only reason that patient will ever get any sleep evet again.  Company Comment : This is a spontaneous case concerning a 16-year-old, male patient with no preexisting conditions, who experienced the unexpected serious (Life-threatening, hospitalization and medically significant) event of cardiac arrest. The event occurred while the patient was sitting at his desk in class and reported in relationship with the administration of mRNA-1273.222 vaccine, however latency could not be assessed due to lack of information. The patient received 4 rounds of Cardiopulmonary Resuscitation at school and transferred to hospital was stabilized. Several investigational tests were done but details not disclosed. No abnormalities were found. An implantable cardioverter-defibrillator was implanted and 6 days after admission, patient was discharged. No further information was disclosed. The benefit-risk relationship of mRNA-1273.222 Vaccine is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a 16-year-old, male patient with no preexisting conditions, who experienced the unexpected serious (Life-threatening, hospitalization and medically significant) event of cardiac arrest. The event occurred while the patient was sitting at his desk in class and reported in relationship with the administration of mRNA-1273.222 vaccine, however latency could not be assessed due to lack of information. The patient received 4 rounds of Cardiopulmonary Resuscitation at school and transferred to hospital was stabilized. Several investigational tests were done but details not disclosed. No abnormalities were found. An implantable cardioverter-defibrillator was implanted and 6 days after admission, patient was discharged. No further information was disclosed. The benefit-risk relationship of mRNA-1273.222 Vaccine is not affected by this report.