Blood clots in his lungs,started to feel that he could hardly breath, but it was not that bad; Fever; Chills; This spontaneous case was reported by a patient and describes the occurrence of PULMONARY THROMBOSIS (Blood clots in his lungs,started to feel that he could hardly breath, but it was not that bad) in a 63-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 029H21B, 031A21A and 024M20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Patient had no Allergies (medications, food, and other products) and patient never had COVID positive test or diagnosis.  Concurrent medical conditions included Diabetes (Diagnosed 8 years ago and Recent change in status such as improvement or worsening was reported as improvement, borderline), Knee arthritis (Diagnosed 3 years ago and recent change in status such as improvement or worsening was reported as improving) and Blood pressure high (Diagnosed 7 years ago and Recent change in status such as improvement or worsening was reported as improving).   On 09-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 10-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 08-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 13-Apr-2022, received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 13-Apr-2022, the patient experienced PYREXIA (Fever) and CHILLS (Chills). On 24-Apr-2022, the patient experienced PULMONARY THROMBOSIS (Blood clots in his lungs,started to feel that he could hardly breath, but it was not that bad) (seriousness criteria hospitalization and medically significant). The patient was hospitalized from sometime in April 2022 to sometime in April 2022 due to PULMONARY THROMBOSIS. The patient was treated with APIXABAN (ELIQUIS) at a dose of 5 milligram and OXYGEN at an unspecified dose and frequency. On 24-Apr-2022, PYREXIA (Fever) and CHILLS (Chills) had resolved. At the time of the report, PULMONARY THROMBOSIS (Blood clots in his lungs,started to feel that he could hardly breath, but it was not that bad) had not resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Patient other vaccines given within 1 month prior to Moderna COVID-19 vaccine (type, brand, lot, route, dose) was reported as shingles on 12-Apr-2022.  It was reported that with first 3 doses patient did not experience any symptoms, but after 2nd booster shot patient started to experience fever and chills for 11 days, on 16-Apr-2022 he started to feel that he could hardly breath, but it was not that bad. On 24-Apr-2022, patient visited ER because he was not able to breath and not even walk 10 steps. Patient was hospitalized 4 days and doctors detected blood clots in his lungs. Currently fever and chills are resolved, patient is not breathing 100 percent well, but he feels better, but blood clots are still ongoing, and doctors will give a follow up on 6 months.   Patient treatment for his symptoms was reported as Eliquis 5mg and oxygen. Patient stated he is under a lot of regular medications, but he could not give the names.  Patient did not experienced Blood lots and could hardly breath in the past. Company comment: This spontaneous case concerns a 63-year-old male patient, with concurrent medical conditions of Diabetes, and Blood pressure high, who experienced unexpected, serious (hospitalized, medically significant) AESI of Pulmonary thrombosis, after receiving a fourth dose of mRNA-1273 vaccine as a second booster dose.  The patient received mRNA-1273 vaccine as the primary COVID-19 vaccine and has received the third dose of mRNA-1273 vaccine as the first booster dose, approximately 4 months before receiving the second booster dose of mRNA-1273 vaccine.  Three days after the second booster, patient started to feel that he could hardly breath, however, it still well tolerated.  However, eleven days after vaccination, the patient was unable to breath and even walk 10 steps prompting emergency room consultation; he was then admitted for further evaluation and management. During hospitalization, doctors detected blood clots in his lungs. Diagnostic test results are not available in this report.  The patient was started with Oxygen therapy, Apixaban (Eliquis) at 5 mg. The event had not resolved. Patient's concurrent medical condition of Diabetes and Blood pressure high could be considered as risk factors for the event. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This spontaneous case concerns a 63-year-old male patient, with concurrent medical conditions of Diabetes, and Blood pressure high, who experienced unexpected, serious (hospitalized, medically significant) AESI of Pulmonary thrombosis, after receiving a fourth dose of mRNA-1273 vaccine as a second booster dose.  The patient received mRNA-1273 vaccine as the primary COVID-19 vaccine and has received the third dose of mRNA-1273 vaccine as the first booster dose, approximately 4 months before receiving the second booster dose of mRNA-1273 vaccine.  Three days after the second booster, patient started to feel that he could hardly breath, however, it still well tolerated.  However, eleven days after vaccination, the patient was unable to breath and even walk 10 steps prompting emergency room consultation; he was then admitted for further evaluation and management. During hospitalization, doctors detected blood clots in his lungs. Diagnostic test results are not available in this report.  The patient was started with Oxygen therapy, Apixaban (Eliquis) at 5 mg. The event had not resolved. Patient's concurrent medical condition of Diabetes and Blood pressure high could be considered as risk factors for the event. The benefit-risk relationship of mRNA-1273 is not affected by this report.