This spontaneous report received via a Regulatory Authority VAERS (Vaccine Adverse Event Reporting System) concerned a 59 year old white, not Hispanic or Latino male. The patient's height, and weight were not reported. The patient's past medical history included: coronary artery bypass graft x4, and concurrent conditions included: HIV, coronary atherosclerosis, depression, benign prostatic hyperplasia, hypertension, hyperlipidemia, and robitussin drug allergy, and other pre-existing medical conditions included: Patient had no current illnesses at the time of vaccination, and never had any adverse event following any previous vaccine. The patient received Covid-19 vaccine ad26.cov2.s (suspension for injection, intramuscular, batch number: 1808980, expiry: unknown) dose was not reported, 1 total administered on 09-APR-2021;15:00 to left arm for an unspecified indication. Concomitant medications included acetylsalicylic acid, amlodipine, bupropion, dolutegravir, dorzolamide hydrochloride/timolol maleate, emtricitabine/tenofovir, ibuprofen, simvastatin, and tamsulosin. On 28-APR-2021;09:00, the patient experienced deep vein thrombosis, peripheral vein occlusion, thrombophlebitis superficial, entire leg red and swollen (peripheral swelling, erythema), 4 plus edema from hip to toes (oedema peripheral) and was hospitalized (date unspecified). The patient was hospitalized for 1 day. Laboratory data on 28-APR-2021 included: fibrin D Dimer increased (NR: not provided) 1,368.00 ng/mL, and ultrasound Doppler abnormal (NR: not provided) venous thrombosis, oedema; occlusive deep venous thrombosis was seen throughout the left lower extremity extending into the left common femoral vein, femoral vein, central great saphenous vein, Profunda femoral vein, popliteal vein, and peroneal veins, flow was seen in the central left external iliac vein and into the inferior vena cava. The thrombus appeared echogenic centrally within the left femoral vein and common femoral vein, suggesting acute on chronic thrombus. Lower extremity edema noted. The action taken with Covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from deep vein thrombosis, peripheral vein occlusion, thrombophlebitis superficial, peripheral swelling, erythema, oedema peripheral, fibrin d dimer increased, and ultrasound doppler abnormal. This report was serious (Hospitalization Caused / Prolonged). Additional information was received from a reporter on 11-MAR-2022. The following information was updated and incorporated into the case narrative: patient demographics (race, ethnicity), pre-existing medical condition, additional reporter HCP added, event time and vaccination time. Upon review, the following information was amended: reporter updated, drug allergy recoded in disease, event description updated, indication corrected. Sender's Comments: V1: Follow up information received in the current version is regarding patient demographics (race, ethnicity), pre-existing medical condition, additional reporter, event time and vaccination time. Upon review, the following information was amended: reporter updated, drug allergy recoded in disease, event description updated, indication corrected. This updated information does not change the prior causality assessment of reported events. 20210515226-Covid-19 vaccine ad26.cov2.s-deep vein thrombosis, peripheral vein occlusion, thrombophlebitis superficial, peripheral swelling, erythema, oedema peripheral, fibrin D Dimer increased, and ultrasound doppler abnormal. This event(s) is considered not related. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There are other factors more likely to be associated with the event(s) than the drug. Specifically: UNDERLYING DISEASE.