Mesenteric vein thrombosis; Mesenteric venous occlusion; This serious case was reported by a consumer via other manufacturer and described the occurrence of mesenteric vein thrombosis in a 41-year-old female patient who received DTPa (Reduced antigen) (Boostrix) (batch number X449Y) for prophylaxis. Co-suspect products included COVID-19 VACCINE PROT. SUBUNIT (NVX COV 2373) (NOVAVAX COVID-19 VACCINE) (batch number 6024MF014A) for covid-19 immunization. Previously administered products included Boostrix (First dose received on an unknown date.), Boostrix (Second dose received on an unknown date.) and Boostrix (Third dose received on an unknown date.). Concurrent medical conditions included hepatic disease and drug allergy (Allergy to codeine and erythromycin). Concomitant products included azathioprine, prednisone, furosemide (Lasix) and spironolactone. On 01-OCT-2024, the patient received the 4th dose of Boostrix (intramuscular) and the 4th dose of NOVAVAX COVID-19 VACCINE (intramuscular). On 02-DEC-2024, 62 days after receiving Boostrix, the patient experienced mesenteric vein thrombosis (Verbatim: Mesenteric vein thrombosis) (serious criteria disability and GSK medically significant) and occlusion mesenteric vein (Verbatim: Mesenteric venous occlusion) (serious criteria disability). The outcome of the mesenteric vein thrombosis and occlusion mesenteric vein were not resolved. It was unknown if the reporter considered the mesenteric vein thrombosis and occlusion mesenteric vein to be related to Boostrix and Boostrix Pre-Filled Syringe Device. The company considered the mesenteric vein thrombosis and occlusion mesenteric vein to be unrelated to Boostrix and Boostrix Pre-Filled Syringe Device. This report is made by GSK without prejudice and does not imply any admission or liability for the incident or its consequences. Additional Information: GSK Receipt Date: 13-JAN-2025 On 01-Oct-2024, the patient received dose 4 of Boostrix and dose 4 of Novavax. It was reported as the patient was not sure if she had the right kind of Tdap listed. her chart showed Tdap-adol/adult-Lot # X449Y. The reaction she believed was to the COVID vaccine. she received imaging several times a year to monitor her liver disease. On 26 September 2024, the ultrasound report showed color doppler imaging demonstrated no portal vein thrombus. Then when she went to visit another clinic on 02 December 2024, the CT scan revealed complete occlusion of the cephalic end of the superior mesenteric vein. For the portal vein thrombosis to go from small to non existent to total clot in the superior mesenteric vein in not even 3 months time did not seem to be a coincidence. The reporter’s causality assessment between the Novavax COVID-19 Vaccine, Adjuvanted (2024 – 2025 Formula), and events mesenteric vein thrombosis and mesenteric venous occlusion was captured as possible.; Sender’s Comments: Mesenteric vein thrombosis and Mesenteric venous occlusion are unlisted events which are considered unrelated to GSK vaccine Boostrix and Boostrix PRE-FILLED SYRINGE DEVICE.