Passing out/in and out of consciousness; Brain aneurism; Blood clot in his brain; Headache immediately/massive headache/out-of-control pain in his head; He couldn't feel his leg; Shaking; Throwing up/Vomiting; Felt like someone hit him with a baseball bat; Dizziness; This case was received via an unknown source (no reference has been entered for a health authority or license partner) on 07-Dec-2021 and was forwarded to Moderna on 08-Dec-2021.    This spontaneous case was reported by a consumer and describes the occurrence of LOSS OF CONSCIOUSNESS (Passing out/in and out of consciousness), ANEURYSM (Brain aneurism), THROMBOSIS (Blood clot in his brain), HEADACHE (Headache immediately/massive headache/out-of-control pain in his head), MUSCULAR WEAKNESS (He couldn't feel his leg), TREMOR (Shaking), VOMITING (Throwing up/Vomiting), FEELING ABNORMAL (Felt like someone hit him with a baseball bat) and DIZZINESS (Dizziness) in a 62-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.     No Medical History information was reported.    On 01-Dec-2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced LOSS OF CONSCIOUSNESS (Passing out/in and out of consciousness) (seriousness criteria hospitalization, medically significant and life threatening), ANEURYSM (Brain aneurism) (seriousness criteria hospitalization, medically significant and life threatening), THROMBOSIS (Blood clot in his brain) (seriousness criteria hospitalization, medically significant and life threatening), HEADACHE (Headache immediately/massive headache/out-of-control pain in his head) (seriousness criteria hospitalization, medically significant and life threatening), MUSCULAR WEAKNESS (He couldn't feel his leg) (seriousness criteria hospitalization, medically significant and life threatening), TREMOR (Shaking) (seriousness criteria hospitalization, medically significant and life threatening), VOMITING (Throwing up/Vomiting) (seriousness criteria hospitalization, medically significant and life threatening), FEELING ABNORMAL (Felt like someone hit him with a baseball bat) (seriousness criteria hospitalization, medically significant and life threatening) and DIZZINESS (Dizziness) (seriousness criteria hospitalization, medically significant and life threatening). The patient was hospitalized on 06-Dec-2021 due to HEADACHE. At the time of the report, LOSS OF CONSCIOUSNESS (Passing out/in and out of consciousness), ANEURYSM (Brain aneurism), THROMBOSIS (Blood clot in his brain), HEADACHE (Headache immediately/massive headache/out-of-control pain in his head), MUSCULAR WEAKNESS (He couldn't feel his leg), TREMOR (Shaking), VOMITING (Throwing up/Vomiting), FEELING ABNORMAL (Felt like someone hit him with a baseball bat) and DIZZINESS (Dizziness) outcome was unknown.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.       No Concomitant medication provided. No treatment medication reported.  The patient was currently on life support. On 07-Dec-2021, the patient had a surgery to open his leg and doctors would udecide if patient had brain surgery. The reporter reported that the patient may not make it.  Company Comment - This case concerns a 62 year old male patient with no relevant medical history, who experienced the serious (life-threatening, hospitalization), unexpected events of loss of consciousness, aneurysm, thrombosis, headache, muscular weakness, tremor, vomiting, feeling abnormal, dizziness. The events occurred on an unknown date after the third dose of mRNA-1273 vaccine. The rechallenge was unknown as this sis the third dose. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.   This case was linked to MOD-2021-406028 (Patient Link).; Sender's Comments: This case concerns a 62 year old male patient with no relevant medical history, who experienced the serious (life-threatening, hospitalization), unexpected events of loss of consciousness, aneurysm, thrombosis, headache, muscular weakness, tremor, vomiting, feeling abnormal, dizziness. The events occurred on an unknown date after the third dose of mRNA-1273 vaccine. The rechallenge was unknown as this sis the third dose. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.