Management of cerebral and splanchnic vein thrombosis associated with thrombocytopenia in subjects previously vaccinated with Vaxzevria (AstraZeneca): a position statement from the Italian Society for the Study of Haemostasis and Thrombosis (SISET)

The emergence of rare thrombotic events associated with thrombocytopenia following vaccination with ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca) has prompted significant concern and regulatory responses. This position statement by the Italian Society for the Study of Haemostasis and Thrombosis (SISET) provides recommendations for the management of cerebral and splanchnic vein thrombosis occurring within 30 days of vaccination. These thrombotic events, provisionally termed Vaxzevria-associated thrombocytopenia thrombotic syndrome (VATTS), predominantly affect younger individuals and present with a high fatality rate. The syndrome shares pathophysiological similarities with heparin-induced thrombocytopenia, as anti-PF4 antibodies have been detected in several cases. Key recommendations include immediate reporting of new cases to national pharmacovigilance authorities, hospitalization in high-intensity care units, and comprehensive diagnostic assessments, including imaging and hematological screening. Therapeutic management should be individualized based on platelet count and coagulation status. Intravenous immunoglobulins and corticosteroids are recommended in cases of severe thrombocytopenia, while anticoagulation should be initiated cautiously, avoiding heparin-based therapies if anti-PF4 antibodies are present. Alternative anticoagulants such as fondaparinux or argatroban should be considered. Plasma exchange may be necessary in refractory cases. While causality between vaccination and VATTS remains under investigation, SISET emphasizes the importance of continued vigilance and structured management to mitigate risks. Given the significant impact of COVID-19 on thrombotic complications, vaccination remains a priority, but awareness and preparedness for rare adverse events are essential to ensure patient safety.