breathing difficulties; lungs looked like chards of glass; blood clots in legs and lung; This spontaneous case was reported by a consumer and describes the occurrence of THROMBOSIS (blood clots in legs and lung), DYSPNOEA (breathing difficulties) and LUNG OPACITY (lungs looked like chards of glass) in a 75-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 007M20A) for COVID-19 vaccination.     The patient's past medical history included Low pulse rate (Patient had an episode of low pulse rate in 2015.) and Pacemaker insertion (cardiac) (History of pacemaker prior to vaccination.). Previously administered products included for Product used for unknown indication: Flu shot (Flu shot in 2020 (Sept/Oct)) in 2020. Past adverse reactions to the above products included No adverse event with Flu shot. Concurrent medical conditions included Seasonal allergy. Concomitant products included ACETYLSALICYLIC ACID (BABY ASPIRIN), PREDNISONE, APIXABAN (ELIQUIS) and OMEPRAZOLE for an unknown indication.    On 28-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 24-Feb-2021, the patient experienced DYSPNOEA (breathing difficulties) (seriousness criterion hospitalization). In 2021, the patient experienced THROMBOSIS (blood clots in legs and lung) (seriousness criteria hospitalization and medically significant) and LUNG OPACITY (lungs looked like chards of glass) (seriousness criterion hospitalization). The patient was hospitalized from 24-Feb-2021 to 02-Mar-2021 due to DYSPNOEA, LUNG OPACITY and THROMBOSIS. At the time of the report, THROMBOSIS (blood clots in legs and lung) and LUNG OPACITY (lungs looked like chards of glass) outcome was unknown and DYSPNOEA (breathing difficulties) had not resolved.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   The patient concomitants includes water pill and treatment medication includes blood thinners on Feb-2021. Patient had no history of blood clots. No consistent medical problems until the vaccination. Patient was able to do most anything that patient wanted to do. This past year was pretty bad. No history of COVID. Went to PCP on Feb 24, 2021 first for breathing difficulties, they sent him to the hospital. Admitted to hospital on Feb 24 2021. They found blood clots in legs and lungs. Caller states hospital said patients lungs looked like chards of glass. Caller states her husband had no history of blood clots. He continued to have problems with breathing that they(HCPs) felt could have been a clot interfering with his breathing. Discharged March 02, 2021. Company comment This regulatory authority case concerns a 75-year-old male patient, with medical history of Pacemaker insertion prior to vaccination, who experienced the unexpected serious (hospitalization) events of THROMBOSIS (hospitalization and medically significant) (AESI), DYSPNOEA and LUNG OPACITY, which occurred approximately 28 days after receiving the first dose of mRNA-1273 vaccine. Patient went to PCP on Feb 24, 2021 first for breathing difficulties, they sent him to the hospital. Admitted to hospital on Feb 24 2021. They found blood clots in legs and lungs. Caller states hospital said patient´s lungs looked like chards of glass. He continued to have problems with breathing that they (HCPs) felt could have been a clot interfering with his breathing. The mentioned medical history remains as a confounder. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.   This case was linked to MOD-2022-494185 (Patient Link).; Sender's Comments: This regulatory authority case concerns a 75-year-old male patient, with medical history of Pacemaker insertion prior to vaccination, who experienced the unexpected serious (hospitalization) events of THROMBOSIS (hospitalization and medically significant) (AESI), DYSPNOEA and LUNG OPACITY, which occurred approximately 28 days after receiving the first dose of mRNA-1273 vaccine. Patient went to PCP on Feb 24, 2021 first for breathing difficulties, they sent him to the hospital. Admitted to hospital on Feb 24 2021. They found blood clots in legs and lungs. Caller states hospital said patient´s lungs looked like chards of glass. He continued to have problems with breathing that they (HCPs) felt could have been a clot interfering with his breathing. The mentioned medical history remains as a confounder. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.