The vaccine is affecting young people; My son felt like he had an aneurysm in his neck/He had pain in the large artery on the right side of his neck like a myocardial inflammation or something; The right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes; On Tuesday, on the right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes; shoulder pain; On Saturday night he was feeling tired and cold; feeling cold; On Saturday his legs were very heavy and had pain, like he had blood clots or thrombosis in his veins; On Saturday his legs were very heavy and had pain; This spontaneous case was reported by a patient and describes the occurrence of THROMBOSIS (On Saturday his legs were very heavy and had pain, like he had blood clots or thrombosis in his veins) and ANEURYSM (My son felt like he had an aneurysm in his neck/He had pain in the large artery on the right side of his neck like a myocardial inflammation or something) in a 23-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 027L21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concomitant products included BUPROPION HYDROCHLORIDE (ZYBAN) for an unknown indication.    On 21-May-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 22-May-2021, the patient experienced THROMBOSIS (On Saturday his legs were very heavy and had pain, like he had blood clots or thrombosis in his veins) (seriousness criterion medically significant), PAIN IN EXTREMITY (On Saturday his legs were very heavy and had pain), FEELING COLD (feeling cold) and FATIGUE (On Saturday night he was feeling tired and cold). On 25-May-2021, the patient experienced ANEURYSM (My son felt like he had an aneurysm in his neck/He had pain in the large artery on the right side of his neck like a myocardial inflammation or something) (seriousness criterion medically significant), NECK PAIN (The right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes), SWELLING (On Tuesday, on the right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes) and ARTHRALGIA (shoulder pain). On an unknown date, the patient experienced VACCINATION COMPLICATION (The vaccine is affecting young people). At the time of the report, THROMBOSIS (On Saturday his legs were very heavy and had pain, like he had blood clots or thrombosis in his veins), ANEURYSM (My son felt like he had an aneurysm in his neck/He had pain in the large artery on the right side of his neck like a myocardial inflammation or something), VACCINATION COMPLICATION (The vaccine is affecting young people), PAIN IN EXTREMITY (On Saturday his legs were very heavy and had pain), NECK PAIN (The right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes), SWELLING (On Tuesday, on the right side of his neck, between the shoulder and neck, on the inside, he felt swelling, pressure pain, dull pain that comes and goes), FEELING COLD (feeling cold), ARTHRALGIA (shoulder pain) and FATIGUE (On Saturday night he was feeling tired and cold) outcome was unknown.            No treatment information was provided.  Company comment: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.   This case was linked to MOD-2021-182543 (Patient Link).; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.