Budd-Chiari syndrome after BNT162b2 mRNA vaccination: two case reports

Budd-Chiari syndrome (BCS) is a rare disease characterised by an obstruction in the hepatic venous outflow. We describe two cases of patients hospitalised a few days after tozinameran vaccination. Liver tests and medical imaging were carried out, and BCS was diagnosed. After treatment including anticoagulant therapy, the first patient improved clinically, unlike the second patient with persistent hepatic thrombosis. According to the WHO-UMC causality assessment system, the vaccine's share was assessed as 'probable' for the first patient as BCS occurred during anticoagulant therapy, and 'possible' for the second patient as no other aetiology was found. Further epidemiological studies are needed to confirm or refute the causal relationship between BCS and tozinameran vaccination.