This spontaneous case was reported by a patient and describes the occurrence of THROMBOSIS (It almost feels like a blood clot or an aneurysm in the back of his head) in a 65-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 009C21A and 045A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. The patient's past medical history included Computerized tomogram thorax in 2007. Previously administered products included for Product used for unknown indication: Arixtra (Patient was taking injection by GlaxoSmithKline for a year or so but they discontinued). Past adverse reactions to the above products included No adverse event with Arixtra. Concurrent medical conditions included Pulmonary thromboembolism (Pulmonary Thromboembolic Disorder. No recent changes in status. 2007 diagnosis by CT scan of lungs) since 2007. Concomitant products included RIVAROXABAN (XARELTO) for an unknown indication. On 18-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 23-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 23-Apr-2021, after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced INAPPROPRIATE SCHEDULE OF PRODUCT ADMINISTRATION (Fist dose taken on 18Mar2021 and second dose was taken on 23Apr2021). In May 2021, the patient experienced FEELING ABNORMAL (Three weeks later, his head felt funny and foggy/It was all in the back of his head. The back of his head felt foggy, his head felt hollow/He had trouble collecting his thoughts). On an unknown date, the patient experienced THROMBOSIS (It almost feels like a blood clot or an aneurysm in the back of his head) (seriousness criterion medically significant), IMPAIRED QUALITY OF LIFE (It is totally impacted his quality of life.), ANEURYSM (It almost feels like a blood clot or an aneurysm in the back of his head) and FATIGUE (really tired). At the time of the report, THROMBOSIS (It almost feels like a blood clot or an aneurysm in the back of his head), FEELING ABNORMAL (Three weeks later, his head felt funny and foggy/It was all in the back of his head. The back of his head felt foggy, his head felt hollow/He had trouble collecting his thoughts), IMPAIRED QUALITY OF LIFE (It is totally impacted his quality of life.), ANEURYSM (It almost feels like a blood clot or an aneurysm in the back of his head) and FATIGUE (really tired) had not resolved and INAPPROPRIATE SCHEDULE OF PRODUCT ADMINISTRATION (Fist dose taken on 18Mar2021 and second dose was taken on 23Apr2021) outcome was unknown. For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments. No other vaccines were given within 1 month prior to Moderna COVID-19 vaccine. Patient had no allergies. Patient never had COVID positive test or diagnosis. The patient reported that he never felt right about three weeks after taking the last one. The patient just knew something was wrong because he knew his body. He did not have any fever or rash. That was really bad for 6 months last year, then that slowed down around end of Dec.. That got better, but then that came back. That was like every day of his life. He had just been coping with that. Patient was a lawyer. That totally impacted his quality of life. Patient further stated that Moderna should hear his story if they were doing any research. His doctor stated he did treat other young patients who were having similar situations. Those patients were 19 and 20 and also experienced that after the second dose. The patient stated he had Pulmonary Thromboembolic Disorder, so might be that is why he was feeling things that other people were not. The patient's doctor did not know what that was back then, but currently his primary care doctor thought it was from the Moderna shot because he had other patients with that. The patient stated that he was able to take his mind of that when he was working. He could feel that more when he was not working. The adverse events caused patient to seek a medical care and he visited doctor. No treatment drug was reported. It was reported that symptoms neither improved nor worsened. Company comment: This spontaneous case concerns a 65-year-old, male patient with medical history of Pulmonary Thromboembolic Disorder (2007), who experienced the unexpected, serious (medically significant) AESI of thrombosis, and other unexpected and expected, non-serious events. The non-serious event feeling abnormal (foggy feeling in head) occurred 3 weeks after receiving the second dose of the mRNA-1273 vaccine. The start dates of the other events were not provided, hence, the onset latency could not be assessed. Of note, the second dose was given 36 days after receiving the first dose of the mRNA-1273 vaccine (inappropriate schedule of product administration). It was reported that 3 weeks after vaccination, the patient's head felt funny and foggy. He had trouble collecting his thoughts, and it was all in the back of his head. The back of his head felt foggy and his head felt hollow. The patient knew something was wrong because he knows his body. He didn't have any fever or rash, but was really tired. It was reported that it was really bad for 6 months and then it 'slowed down' around end of Dec. which was approximately 8 months after vaccination. The symptoms got better but then it recurred. The symptoms were continuous every day and the patient had been coping with it. It was reported that it had totally impacted his quality of life. It was also reported that the symptoms almost felt like a blood clot or an aneurysm in the back of his head. The patient was able to take his mind of it when he was working but can feel it more when he was not working. The patient sought consultation, however, no information was provided regarding diagnostic test/s and treatment. It was reported that the doctor thought the symptoms were due to the vaccine because he's had other patients with similar condition. The history of Pulmonary Thromboembolic Disorder remains a confounder for the event thrombosis. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report. Sender's Comments: This spontaneous case concerns a 65-year-old, male patient with medical history of Pulmonary Thromboembolic Disorder (2007), who experienced the unexpected, serious (medically significant) AESI of thrombosis, and other unexpected and expected, non-serious events. The non-serious event feeling abnormal (foggy feeling in head) occurred 3 weeks after receiving the second dose of the mRNA-1273 vaccine. The start dates of the other events were not provided, hence, the onset latency could not be assessed. Of note, the second dose was given 36 days after receiving the first dose of the mRNA-1273 vaccine (inappropriate schedule of product administration). It was reported that 3 weeks after vaccination, the patient's head felt funny and foggy. He had trouble collecting his thoughts, and it was all in the back of his head. The back of his head felt foggy and his head felt hollow. The patient knew something was wrong because he knows his body. He didn't have any fever or rash, but was really tired. It was reported that it was really bad for 6 months and then it 'slowed down' around end of Dec. which was approximately 8 months after vaccination. The symptoms got better but then it recurred. The symptoms were continuous every day and the patient had been coping with it. It was reported that it had totally impacted his quality of life. It was also reported that the symptoms almost felt like a blood clot or an aneurysm in the back of his head. The patient was able to take his mind of it when he was working but can feel it more when he was not working. The patient sought consultation, however, no information was provided regarding diagnostic test/s and treatment. It was reported that the doctor thought the symptoms were due to the vaccine because he's had other patients with similar condition. The history of Pulmonary Thromboembolic Disorder remains a confounder for the event thrombosis. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.