DVT (LEFT CALF); PULMONARY EMBOLISM (BOTH LUNGS); ATRIAL FIBRILLATION; BLOOD CLOT IN RIGHT VENTRICLE; This spontaneous report was received from a consumer (patient's wife) and concerned a 68 year old male. The patient's weight was 250 pounds and was obese (body mass index 40) and sedentary. His height was not provided. The patient's concurrent conditions included high blood pressure, and 2 gout attacks in the last 8 months. The last gout attack was 2 weeks ago in the left foot. There was no history of clots or atrial fibrillation. He had a strong family history of thrombosis: his father had 2 episodes of deep vein thrombosis and his mother had a pulmonary embolism. No testing to identify any familial clotting issues have been performed. The patient developed a cough starting 29-MAR-2021 and, prior to vaccination, took a COVID-19 test on 31-MAR-2021 which was negative. On 02-APR-2021 a rapid COVID-19 test also came back negative.  The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 043A21A, and expiry: UNKNOWN) on 02-APR-2021 at approximately 19:00 in the left arm for prophylactic vaccination. Concomitant medications included amlodipine, hydrochlorothiazide, and losartan for high blood pressure. On 03-APR-2021, the patient's cough persisted but had not worsened and he developed pain in the ribs on the right. His wife checked his pulse, which seemed fast and irregular. His respiratory rate was 22 breaths per minute and his oxygen saturation with a home pulse oximeter was in the 70s. He was not in distress at the time. The patient called his physician and the doctor suggested to go to Emergency room. The patient went to Emergency room at approximately 10:00. An echocardiogram revealed a number of clots in the right ventricle which were "bouncing all around". He was also found to be in atrial fibrillation which the doctors said was secondary to the ventricular clots. Unspecified tests revealed a saddle pulmonary embolus and a deep vein thrombosis on the left.  He was diagnosed with deep vein thrombosis (left calf), pulmonary embolism (both lungs), blood clots in right ventricle and atrial fibrillation. Platelet count was not known by the reporter; it is unknown if  D-dimer and fibrinogen levels were performed.  He underwent emergency surgery at 19:00, during which most of the ventricular clots and the pulmonary embolism were removed. He was placed on heparin after the surgery. He spent 5 days in the Intensive Care Unit (ICU) and 2 additional days in the hospital. The patient was discharged from the hospital after 1 week and had recovered from the events of deep vein thrombosis (left calf), pulmonary embolism (both lungs), atrial fibrillation, and blood clots in right ventricle.  The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The reporter did not believe that the covid-19 vaccine ad26.cov2.s had caused deep vein thrombosis (left calf), pulmonary embolism (both lungs), atrial fibrillation, and blood clot in right ventricle This report was serious (Hospitalization Caused / Prolonged, and Other Medically Important Condition).; Sender's Comments: V0:  a 68-year-old male experienced left deep vein thrombosis, saddle pulmonary embolism, right ventricular thrombosis, and atrial fibrillation, approximately 15 hours after receiving the Janssen COVID-19 vaccine for prevention of COVID-19 infection.  The patient has a history of hypertension, is obese (BMI 40) and has a strong family history of blood clots.  He tested negative for COVID 2 days before and the day of vaccine administration.  He developed a cough 4 days prior to vaccination. The morning after vaccination, he developed right rib pain; his heart rate was rapid and irregular, and oxygen saturation with home pulse oximeter was in the 70s.  Upon arrival in the emergency room, he was found to have clots in the right cardiac ventricle, a saddle pulmonary embolus, left deep vein thrombosis and new-onset atrial fibrillation.  He underwent surgery for removal of the ventricular clots and pulmonary embolism.  No laboratory details were provided.  Given the symptoms which pre-dated vaccine administration,  the short latency between the vaccine administration and the event, and multiple risk factors for embolism and thrombosis (family history, obesity, sedentary nature), the events are assessed as inconsistent with the causal association to immunization, per the WHO causality classification for adverse events following immunization. Therefore, company causality is considered not related to the Janssen COVID-19 vaccine.